Transient body fluid accumulation and enhanced NKCC2 expression in gerbils with brain infarction.

BACKGROUND: Enhanced expression of a kidney-specific sodium co-transporter (NKCC2: Na-K-2Cl co-transporter) in the thick ascending limb of Henle has been identified in rat models of congestive heart failure and liver cirrhosis, suggesting that high NKCC2 expression underlies edema formation. An increased abundance of NKCC2, however, has also been noted in rats with the syndrome of inappropriate secretion of antidiuretic hormone; hyponatremia without edema. In the present study, we examined NKCC2 expression in non-edematous disease, such as a brain infarction, and investigated the physiological and/or pathological characterization of NKCC2 expression. METHODS: We initially examined NKCC2 expression in an animal model of brain infarction. Mongolian gerbils (around 60 g body weight) underwent bilateral clamping of the common carotid arteries for 5 min for the induction of brain infarction. NKCC2 and apical water channel (AQP2) protein levels in the collecting duct were examined by Western blotting in kidney tissues 2, 7, and 14 days after the brain infarction. Gerbils with brain infarction were then fed either a normal low-sodium diet (0.3 g/kg/day) or a high-sodium diet (3.0 g/kg/day), and body weight, urine volume and urinary osmolality were examined daily. Blood parameters were measured on day 14 after the brain infarction. RESULTS: Histochemical examination of the brain confirmed the presence of brain infarction, as manifested by altered cresyl violet staining in the hippocampus. Protein levels of NKCC2 were significantly increased in gerbils with brain infarction on days 2 and 7 after brain infarction, whereas AQP2 protein signals remained unaltered. However, the increased NKCC2 intensity disappeared on day 14. Body weight gain was slightly, but significantly greater in gerbils with brain infarction than in sham-operated gerbils up to 7 days after the brain infarction. The high-sodium diet resulted in significant urinary concentration and enhanced weight gain in infarcted gerbils. CONCLUSION: We noted increased NKCC2 abundance in non-edematous disease, which enhanced body fluid accumulation, likely via the sodium loading-dependent concentration of the urine. These results suggest that the physiological process of edema formation is based on specific NKCC2 expression. The transient duration of these findings in the present animal model suggests two different characteristics of specific NKCC2 expression, an immediate, transient appearance as a common response in serious conditions and more chronic expression that leads to edema formation.

Residual urinary concentrating ability and AQP2 expression in a rat model for chronic renal failure.

BACKGROUND: In chronic renal failure (CRF), a defect in urinary concentrating ability develops gradually as the renal failure progresses. Although several molecular mechanisms associated with renal urinary concentration are reported to be impaired in a rat model for renal failure, the mechanisms underlying residual urinary concentration ability in CRF remain to be elucidated. METHODS: Rats that underwent an 8-week recovery period after 5/6 nephrectomy were used as the model for CRF. Urinary concentration was induced by 24-hour water restriction. Plasma osmolality and arginine vasopressin (AVP) were measured from blood sampled by inserting a catheter into the femoral artery before and after the water restriction. AQP2 mRNA expression in the inner medulla was examined by competitive PCR and in situ hybridization, and protein expression, by Western blotting. Rats that underwent sham operation were used as control. RESULTS: Water restriction significantly reduced urine volume and increased urine osmolality in CRF rats, although such changes were much less than those in sham-operated rats. Plasma AVP was elevated at the basal condition, and further elevation was noted after water restriction. AQP2 mRNA signals were significantly intensified by water restriction even in CRF rats, although the increase was limited as in the case of urine osmolality. Western blotting also showed a small but significant enhancement of protein signals in response to water restriction in CRF rats. CONCLUSIONS: We noted a weak but significant response of AQP2 expression to dehydration in CRF rats. This response in the collecting duct may be one of the factors contributing to residual urinary concentrating ability in CRF.

Water-soluble extracts from Angelica acutiloba Kitagawa enhance hematopoiesis by activating immature erythroid cells in mice with 5-fluorouracil-induced anemia.

The extract from the root of Angelica acutiloba Kitagawa (AR), which is used as herbal medicine in Japan, has been reported to be clinically effective for postmenstrual blood loss and erythropoietin (EPO)-resistant anemia in chronic renal failure, although the pharmacological mechanisms underlying its clinical efficacy are unknown. We prepared an animal model of anemia by bolus injection of 5-fluorouracil (5FU) at 150 mg/kg to mice (8- to 12-week-old female C57BL/6J), and then administered orally the water-soluble fraction of AR to the anemic mice for 10 days. After confirming the anti-anemic effect of the water-soluble fraction of AR (AR-3) containing polysaccharides, we examined the effects of AR-3 on immature erythroid cell activity, EPO production, and plasma cytokine levels. AR-3 administration at 50 mg/kg activated erythroid progenitor cells in bone marrow on day 10, increased the percentage of peripheral reticulocytes in red blood cells on day 15, and led to the recovery of red blood cell count to a value that was almost equal to the basal level on day 20. Although EPO production, which was determined by examining EPO mRNA expression in kidney and liver, remained unaltered by AR-3 administration, this treatment significantly lowered plasma interferon-gamma level, which may suppress the activity of erythroid progenitor cells. These results suggest that the polysaccharides in AR promote hematopoiesis by activating immature erythroid cells, in part, by suppressing cytokine secretion. Since the hematopoietic effect was achieved by high-dose AR-3, identification of specific polysaccharides is still required for the development of a novel medicine for anemia caused by a malignancy or chemotherapy.

Effects of Ca2+ antagonists on motor activity and the dopaminergic system in aged mice.

We investigated the effects of the Ca(2+) antagonist nilvadipine on the dopaminergic system and motor activity in aged mice, in comparison with an other Ca(2+) antagonist, amlodipine. Furthermore, we examined the close correlation between the dopaminergic system and motor activity during the aging process. Striatal dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) contents were measured in 2-, 4-, 8-, 18- and 36-week-old mice. Behavioral tests (pole and catalepsy test) were performed with 4- and 36-week-old mice. Nilvadipine or amlodipine was administered intraperitoneally twice a day for 3 consecutive days to 30-36-week-old mice. The striatal dopamine, DOPAC and HVA contents were examined and behavioral tests were performed 1h after the last injection of each Ca(2+) antagonist. The dopamine, DOPAC and HVA contents in 2-week-old mice were significantly decreased in the striatum, as compared with 4-week-old animals. Thereafter, age-related increases in the dopamine, DOPAC and HVA contents were observed from 4 to 18 weeks old. However, in 36-week-old mice, the dopamine and DOPAC contents were reduced in the striatum, as compared with 18-week-old animals. Age-related decreases in motor function between 5- and 36-week-old mice were observed in both pole test and catalepsy tests. On the other hand, nilvalipine treatment produced a significant and dose-dependent increase in the striatal dopamine and DOPAC contents in 30-36-week-old mice. In contrast, no significant changes were observed in the striatal dopamine content in amlodipine-treated mice, although this drug showed a significant and dose-dependent increase in the striatal DOPAC and HVA content. In our behavioral study, nilvadipine also showed a significant and dose-dependent inhibition against motor deficits in 30-36-week-old mice. In contrast, amlodipine showed no significant effect on motor deficits in 30-36-week-old mice. The present study demonstrated that nilvadipine has a protective effect against the deficits in both the striatal dopaminergic system and motor activity in aged mice. Our study also suggested that the beneficial effect of nilvadipine against motor abnormalities may be mediated by a protective effect against the reduced activity of the dopaminergic system in aged mice. These results suggested that nilvadipine may offer a new approach for the treatment of hypobulia in aged humans.

Pulse wave velocity and the second derivative of the finger photoplethysmogram in treated hypertensive patients: their relationship and associating factors.

OBJECTIVES: To clarify the factors influencing two measures of arterial stiffness, pulse wave velocity (PWV) and the second derivative of the finger photoplethysmogram (SDPTG), and to evaluate their relationship in treated hypertensive subjects. SUBJECTS AND METHODS: The subjects were 294 hypertensive patients aged 32-91 years (mean, 61.4 +/- 10.5 years). After blood pressure (BP) was measured, carotid-femoral PWV and SDPTG were recorded with the subjects in the supine position, with the aid of an automatic device. For assessing SDPTG, we focused mainly on the ratios of the absolute value of the height of the early negative 'b' wave (B) and that of the late re-decreasing 'd' wave (D) to that of the initial positive 'a' wave (A), namely the B : A and D : A ratios, and the aging index (AGI). Factors influencing PWV and SDPTG indices, and the relationship between PWV and SDPTG indices were evaluated by bivariate and multivariate analyses. RESULTS: According to multiple linear regression analysis, age, systolic blood pressure (SBP), and heart rate (HR) were variables independently and positively correlated with PWV. The age and BP were significantly and independently related to SDPTG indices; there were positive correlations with the D : A ratio and AGI, and negative correlations with the B : A ratio. HR was correlated negatively with the D : A ratio and AGI, and positively with the B : A ratio. According to multiple logistic regression analysis, adjusted-odds ratios of high PWV, low B : A ratio, high D : A ratio, and high AGI were significantly elevated among the elderly and among the subjects with uncontrolled BP. Although PWV and the SDPTG indices were associated with common factors, including age and BP, bivariate analysis revealed that they were only weakly correlated with each other. CONCLUSIONS: The results suggest that in hypertensive patients, PWV and SDPTG provide different information about arterial properties at central and peripheral sites.

Therapeutic effects of evening administration of guanabenz and clonidine on morning hypertension: evaluation using home-based blood pressure measurements.

OBJECTIVE: To clarify the effects of bedtime administration of the centrally acting alpha(2)-agonists, guanabenz and clonidine, on morning hypertension. METHODS: Patients with morning hypertension were assigned to receive once-daily evening administration of guanabenz (2 mg/day, n = 81; 4 mg/day, n = 2) or clonidine (75 microg/day, n = 40; 150 microg/day, n = 10) for 4 weeks, and the blood pressure (BP)-lowering effects of these drugs in the morning and evening were evaluated by assessing self-monitored BP in the home environment. The subjects were then subdivided into different groups according to their evening BP, and the effects of guanabenz and clonidine on evening BP were evaluated further for each group. In addition, as a substitute for the trough/peak ratio, the evening/morning (E/M) ratio was calculated to assess the duration of action of the two alpha(2)-agonists. RESULTS: Evening dosing with guanabenz or clonidine lowered morning BP significantly. Both drugs decreased evening BP in the subgroup of subjects with a high evening BP, but not in those with a normal evening BP. The individual E/M ratios for guanabenz, but not for clonidine, were significantly greater in those with a high evening BP than in those with a normal evening BP. In the early treatment period, treatment with guanabenz resulted in a higher diastolic E/M ratio in those subjects with a high evening diastolic BP than did treatment with clonidine. CONCLUSION: The results suggest that evening administration of the central alpha(2)-agonists guanabenz and clonidine effectively suppresses the morning BP elevation in treated hypertensive patients.

Prognostic significance of the nocturnal decline in blood pressure in individuals with and without high 24-h blood pressure: the Ohasama study.

OBJECTIVE: To examine the relationship between the normal nocturnal decline in blood pressure and the risk of cardiovascular mortality in individuals with and without high 24-h blood pressure values. METHODS: We obtained 24-h ambulatory blood pressure readings from 1542 residents of Ohasama, Japan, who were aged 40 years or more and were representative of the Japanese general population. We then followed up their survival for a mean of 9.2 years. The relationship was analysed using a Cox proportional hazards model adjusted for possible confounding factors. RESULTS: There was a linear relationship between the nocturnal decline in blood pressure and cardiovascular mortality. On average, each 5% decrease in the decline in nocturnal systolic/diastolic blood pressure was associated with an approximately 20% greater risk of cardiovascular mortality. There were no significant interactions for the risk between 24-h systolic/diastolic blood pressure values and continuous values for the nocturnal decline in blood pressure ( for interaction 0.6). Even when 24-h blood pressure values were within the normal range ( 135/80 mmHg, average 118/69 mmHg), diminished nocturnal decreases in systolic/diastolic blood pressure were associated with an increased risk of cardiovascular mortality. CONCLUSIONS: This is the first study to demonstrate that a diminished nocturnal decline in blood pressure is a risk factor for cardiovascular mortality, independent of the overall blood pressure load during a 24-h period, in the general population.

Angiotensin-converting enzyme I/D polymorphism and hypertension: the Ohasama study.

OBJECTIVE: Angiotensin-converting enzyme (ACE) I/D polymorphism in intron 16 of the ACE gene was analyzed in a general Japanese population in relation to self-blood pressure (BP) measurement at home (home BP) and ambulatory BP monitoring (ABPM) to determine the association between genetic variants of this polymorphism and hypertension. DESIGN: A cross-sectional study. METHODS AND RESULTS: We genotyped the ACE I/D polymorphism in 1245 subjects with home BP and 803 subjects with ABPM in Ohasama, a rural community in Japan. All the subjects were 40 years of age and over, and gave written informed consent for the present genetic analysis. Hypertensive subjects were defined as those receiving antihypertensive drugs and those who had a home BP higher than 135 mmHg in systole and/or higher than 85 mmHg in diastole. The frequencies of the II, ID, and DD genotypes in these Japanese subjects were 0.45, 0.45, and 0.10, indicating a lower frequency of the D allele (0.33) than in Caucasians. There was no significant difference of BP level, prevalence of hypertension or nocturnal decline in BP among the genotypes. There were no differences in the prevalence of previous cardiovascular disease, age, body mass index, male gender, smoking, or biochemical and hormonal parameters among the three genotypes. CONCLUSION: The present results indicate the absence of direct effects of the ACE D-allele on BP level, prevalence of hypertension, prevalence of cardiovascular disease, and circadian BP variation. We conclude there is little association between ACE I/D polymorphism and hypertension in the general Japanese population.

Genotypes of the betaENaC gene have little influence on blood pressure level in the Japanese population.

The gene for the beta-subunit of the epithelial sodium channel (betaENaC) is one of the most prominent candidate genes being analyzed for an association with human essential hypertension. It is known that a deletion or alteration of PY motif in exon 12 of betaENaC is responsible for Liddle's syndrome. Although the localization of genetic polymorphisms of betaENaC is unique to each population, intensive analysis of individuals of white and African ancestry has demonstrated that genetic variants are localized in exons 8 and 12, with two frequent polymorphisms, G442V in exon 8 and T594M in exon 12. These two mutations are both found in individuals of African ancestry, and might be associated with elevated blood pressure (BP). Previously, we have screened the last two-thirds of exon 12 in the Japanese population, and demonstrated the absence of the T594M mutation and the presence of a novel P592S mutation. In the present study, we further examined the rest of exon 12 and exon 8 in a general population from Ohasama, Japan (the Ohasama Study), using single-strand conformational polymorphism (SSCP) analysis. We screened 803 subjects randomly selected from the representative participants, who measured their home and casual BP. The PCR products presenting a shift in SSCP gels, as well as controls, were directly sequenced by autoanalyzer to identify the mutation. A novel gel shift was noted in exon 12 (n = 8) and sequencing identified a polymorphism at codon Ser 520, leading to no change in amino acid sequence (G77576C TCG-->TCC). In exon 8, all three SSCP variants were heterogynous for V434M (GTG-->ATG), which is coincident with a rare polymorphism in whites. The G442V mutation, however, was absent from the Japanese population. A novel mutation of exon 12 was not associated with a significant difference in clinical features. These results indicate that Japanese people possess three polymorphisms in exon 12, all of which are unique, and one in exon 8. These genetic variants of betaENaC may not influence the BP level of Japanese people.

T+31C polymorphism of angiotensinogen gene and nocturnal blood pressure decline: the Ohasama study.

BACKGROUND: We assessed the association between several polymorphisms of angiotensinogen gene (AGT) and essential hypertension using ambulatory blood pressure (BP). METHODS: We recruited 802 subjects in a rural Japanese community who were aged >40 years and who gave written informed consent for monitoring of their ambulatory BP and genetic analysis (the Ohasama Study). As a polymorphism of AGT, T+31C, which is in complete linkage disequilibrium with M235T, was determined using the TaqMan polymerase chain reaction method. RESULTS: The genotype distribution of AGT/T-+31C in the Ohasama Study was similar to that in another large Japanese population. Although there was no significant difference in 24-h and daytime ambulatory BP values, the nighttime BP was significantly lower in the subjects with TT, resulting in greater decline of nocturnal systolic (P = .090) and diastolic (P = .025) BP in subjects with TT. CONCLUSIONS: AGT/T+31C is associated with the circadian BP variation but not with BP level in the Japanese general population.

T+31C polymorphism (M235T) of the angiotensinogen gene and home blood pressure in the Japanese general population: the Ohasama Study.

The angiotensinogen (AGT) gene polymorphism M235T (a methionine to threonine amino acid substitution) has been investigated in association with essential hypertension (EHT) based on conventional measurement of blood pressure (BP); however, the results have been inconsistent. Recently, we have been conducting lines of genetic analysis on a general population of Ohasama Town in Iwate Prefecture, Japan, who measured their BP at home (Ohasama genetic analysis and home BP project). We here assessed the association between AGT M235T polymorphism and hypertension within the same population (1,245 subjects aged 40 years and over). AGT M235T polymorphism was determined by genotyping the AGT T+31C polymorphism, which has complete disequilibrium with the AGT M235T polymorphism. We defined subjects as hypertensive if they were being treated with antihypertensive medication and/or had home BP values of more than 135 mmHg in systole and/or 85 mmHg in diastole. The genotype frequencies were similar to those in previous Japanese studies. There was no significant difference among the genotypes in home BP values (p = 0.63/0.74 for systolic/diastolic blood pressure) or in prevalence of hypertension (MM: 44.7%; MT: 42.3%; TT: 39.6%; p = 0.61). No difference was noted in the frequency of familial history of hypertension. Pulse pressure, however, was significantly different among the genotypes (p = 0.049), and this association was prominent in the older (age260) population (p = 0.0018), but not noted in the younger population (60 > age > or = 40). In conclusion, the present analysis confirmed the lack of a significant effect of AGT M235T polymorphism on blood pressure level, but the difference in pulse pressure in the older population suggests that further investigations of this polymorphism should be made in the Japanese population.

CYP11B2 polymorphisms and home blood pressure in a population-based cohort in Japanese: the Ohasama study.

Genetic polymorphisms of the aldosterone synthase gene (CYP11B2) have been major targets of studies into the genetic factors involved in hypertension. We have identified three genetic variants of CYP11B2, -344C/T at the promoter region, a conversion in intron 2 from the CYP11B2 sequence to the CYP11B1 sequence, and R173K in exon 3, in the Japanese population. -344C/T and R173K were in complete linkage disequilibrium in CYP11B2, and -344C/T was in strong, but not complete, linkage disequilibrium with the polymorphism in intron 2. Thus, two genetic polymorphisms, -344C/T and the gene conversion in intron 2, were investigated in association with home blood pressure (BP) values and clinical parameters in 1,242 subjects aged 40 and over in Ohasama, a rural Japanese community. Hypertension was defined as being treated with antihypertensive medication and/or having home BP values of more than 135 mmHg in systole and/or 85 mmHg in diastole. The results demonstrated that the -344T allele was significantly associated with increased prevalence of hypertension (p=0.015 in multiple logistic regression analysis, adjusted by age, gender, BMI, and smoking status), though BP level was unaltered. This allele was also significantly related to the prevalence of cardiovascular diseases in the older population (60 < or = age, p=0.014). The resting polymorphism, a gene conversion in CYP11B2 intron 2, was not associated with any clinical parameters. Therefore, -344C/T polymorphism in CYP11B2 was considered an independent genetic factor possibly associated with hypertension or atherosclerotic diseases in the Japanese population.

A/C1166 gene polymorphism of the angiotensin II type 1 receptor (AT1) and ambulatory blood pressure: the Ohasama Study.

We previously investigated the relation between hypertension and each of three major genetic polymorphisms in the renin-angiotensin (AGT)-aldosterone system (R-A-A), AGT M235T, angiotensin convert enzyme (ACE) I/D, and CYP11B2 -344C/T, by means of ambulatory blood pressure (ABP) monitoring in a general Japanese population (the Ohasama Study). A/C1166 gene polymorphism in the 3' untranslated region of the angiotensin II type 1 receptor (AT1) gene is the final remaining major target in R-A-A to be examined in the Ohasama Study population. In the present study, the AT1 A/C1166 polymorphism was genotyped by the TaqMan polymerase chain reaction (PCR) method or restriction fragment length polymorphism (RFLP) in 802 Japanese subjects aged 40 and over, who were previously genotyped for the AGT M235T, ACE D/I, CYP11B2 -344C/T polymorphisms. The AA genotype, AC genotype, and CC genotype were present in 678 (84.5%), 121 (15.1%), and 3 (0.4%) of subjects, respectively. Since the frequency of the C allele was quite low (0.079), the genotypes were classified according to the presence or absence of the C allele. Although daytime blood pressure (BP) was higher in subjects with the C allele, the difference was not statistically significant after adjusting for age, gender, body mass index, and smoking status. No significant difference was noted in the prevalence of cardiovascular diseases or nocturnal BP decline between the two groups. These results indicated that AT1 A/C1166 polymorphism was not associated with any clinical parameters associated with hypertension or atherosclerosis in the Japanese population.

Protective effects of neuronal nitric oxide synthase inhibitor in mouse brain against MPTP neurotoxicity: an immunohistological study.

We recently reported that neuronal nitric oxide synthase (nNOS) inhibitor, 7-nitroindazole, can protect against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in mice. It protected against both dopamine depletions and tyrosine hydroxylase (TH) positive neuron decreases in the mouse brain. In the present study, we further examined whether 7-nitroindazole can also protect against the alterations of TH-, microtubule-associated protein 2a,b (MAP2)-, glial fibrillary acidic protein (GFAP)-, parvalbumin (PV)-, dopamine transporter (DAT)-, nNOS- or endothelial NOS (eNOS)-positive cells, in comparison with pargyline as a relatively selective inhibitor of the monoamine oxidase-B (MAO-B). The present study showed that nNOS inhibitor as well as MAO-B inhibitor has a dose-dependent protective effect against MPTP-induced striatal dopamine and DOPAC depletion in mice. Furthermore, the present study revealed that 7-nitroindazole and pargyline can protect the alterations of immunohistochemical changes in the striatum and substantia nigra after MPTP treatment. These protective effects may be, at least in part, produced by the reduction of neuronally derived NO and peroxynitrite caused by MPTP. Our results also demonstrate that MPTP can cause functional damage of interneurons in the substantia nigra. These results suggest the possibility that nNOS inhibitors as well as MAO-B inhibitors may be therapeutically useful in neurodegenerative diseases such as Parkinson's disease. Thus our present results provide valuable information for the pathogenesis of degeneration of the nigrostriatal dopaminergic neuronal pathway.

Heart rate measurement and outcome.

Previous studies on the predictive value of heart rate and heart rate variability for the risk of cardiovascular disease remains controversial. Since heart rate is known to be variable with several physical and mental stresses, the inconclusive nature of previous studies might reflect the difference in accuracy and reproducibility of the heart rate measurement. In the Ohasama study, which has been conducted since 1985 in the northern part of Japan, home measurements and ambulatory monitoring of heart rate as well as blood pressure were examined with special reference to cardiovascular mortality. Heart rate measured at home and averaged for 21 days was shown to be linearly associated with cardiovascular mortality, while heart rate variability (standard deviation of daytime ambulatory heart rate measured every 30 min) inversely correlated with cardiovascular mortality. In conclusion, heart rate and heart rate variability must not be overlooked when evaluating hypertension.

Urinary concentration defect and limited expression of sodium cotransporter, rBSC1, in a rat model of chronic renal failure.

BACKGROUND: Renal urinary concentration is associated with enhanced expression of sodium cotransporter (rBSC1) in thick ascending limb of Henle. Overexpression of rBSC1 was reported recently in hypertrophied nephrons after unilateral nephrectomy (UNX) and in kidney isografts. Since urinary concentration defect and hypertrophy of residual nephrons are major manifestations of chronic renal failure (CRF), we investigated the rBSC1 signals for RNA and protein in a rat model of CRF. METHODS: Rats underwent 5/6 nephrectomy and examined 8 weeks after operation. rBSC1 mRNA was examined by competitive PCR and in situ hybridization, and rBSC1 protein signals by western blotting and immunohistochemistry. Rats that underwent sham-operation, UNX, or 5/6 nephrectomy followed by a 3-week recovery period (acute renal failure), were used as control. Water intake was restricted for 24 h in subgroups of control and CRF rats. RESULTS: Microscopic examination showed hypertrophy of residual nephrons in both UNX and CRF rats. Signals for rBSC1 mRNA and protein were enhanced at basal condition only in rats with UNX. Under basal conditions, CRF rats demonstrated low urinary osmolality in spite of high plasma arginine vasopressin levels. Water restriction resulted in increased signals for rBSC1 mRNA and protein and concentration of urine in sham-operated rats, but such increases were absent and urinary concentration was incomplete in CRF rats. CONCLUSIONS: Compensatory overexpression and upregulation of rBSC1 expression in response to dehydration are both absent in CRF rats. These limitations are thought to be the underlying mechanisms of urinary concentrating defect seen in CRF.

Lithium effectively complements vasopressin V2 receptor antagonist in the treatment of hyponatraemia of SIADH rats.

BACKGROUND: Although, pharmacological intervention with a selective arginine vasopressin (AVP) V(2) receptor antagonist has been demonstrated to be effective for syndrome of inappropriate secretion of antidiuretic hormone (SIADH), its long-term administration has some therapeutic limitations. Lithium, a drug for bipolar disorders, has been known to cause nephrogenic diabetes insipidus by reducing kidney-specific apical water channel, aquaporin 2 (AQP2) expression in the collecting ducts. However, its pharmacological efficacy for SIADH still remains to be elucidated. METHODS: Hyponatraemia was induced in male Sprague-Dawley rats by water loading and subcutaneous infusion of 1-deamino-8-D-arginine vasopressin. For the treatment, lithium chloride (LiCl) was administered singly or in combination with OPC-31260 and/or furosemide for 7 days. Protein expression of AQP2 was examined by western blotting at the end of the observation period. RESULTS: The LiCl administration elevated serum sodium levels in a dose-dependent manner. The therapeutic effect started 3 days after the initial administration and gradually increased. Western blot analysis at the end of the treatment demonstrated dose-dependent reduction of AQP2 protein expression. Additional administration of LiCl (100 mg/kg/day, the dose demonstrated to maintain serum lithium concentration within therapeutic range) to low dose OPC-31260 maintained well the initial elevation of serum sodium level during the treatment. Western blot analysis after combination therapy demonstrated the absence of re-increase in AQP2 expression noted at the end of OPC-31260 treatment. However, further additive effect could not be obtained even when both LiCl and furosemide were added together to low dose OPC-31260. CONCLUSIONS: Although the single effect of therapeutic dose of lithium was weak, it effectively and safely compensated for the therapeutic limitations of a low dose of AVP V(2) receptor antagonist for SIADH by reducing AQP2 expression.

Investigation of major genetic polymorphisms in the Renin-Angiotensin-aldosterone system in subjects with young-onset hypertension selected by a targeted-screening system at university.

Although polymorphisms in renin-angiotensin-aldosterone (RAA) system genes for angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), angiotensin II type 1 receptor (AT1 A/C1166), and aldosterone synthase (CYP11B2-344T/C) have been major targets for genetic investigation in association with essential hypertension (EH), the influence of these genetic factors is still to be determined. Because patients with young-onset EH are thought to possess a stronger genetic background than EH patients who show elevated BP relatively late in life, the targeted screening of hypertensive students in Tohoku University was completed for the selection of subjects for genetic investigation. Out of 16,434 students (12,794 males and 3,670 females) younger than 30, 22 students showed a high blood pressure (BP) (systolic and diastolic BP of 140 and/or 90 mmHg or greater, respectively, on two occasions and more than 135 and/or 85 mmHg, respectively, at a third measurement during casual BP measurements at the Tohoku University Health Center. These 22 students were asked to measure their BP at home (HBP). Six of the students had a systolic HBP of more than 135 mmHg and/or a diastolic HBP of more than 85 mmHg, and these students subsequently received medical examinations at Tohoku University Hospital and were diagnosed with EH. Genotyping for the four major genetic polymorphisms mentioned above was performed on the six students with EH and on 12 of the remaining 16 students whose HBP was within the normal range (white coat hypertension: WCH). Neither the EH nor the WCH students showed a different distribution of genotypes and allelic frequencies, compared to those found in the general Japanese population. Hence, the present study suggests that none of the major genetic polymorphisms in the RAA system strongly influence the onset of EH.

Steroid resistance in prolonged type I membranoproliferative glomerulonephritis and accelerated disease remission after steroid withdrawal.

Two cases of severe proteinuria and hypocomplementemia were referred to our out patient clinic for continuous follow-up. Initial onset of clinical symptoms was at the age of 15 years in both cases. They had already been diagnosed as type I membranoproliferative glomerulonephritis (type I MPGN) by renal biopsy when oral prednisolone administration had been initiated. Several courses of steroid pulse therapy were performed for the flares of the disease, resulting in only temporary amelioration of renal symptoms. Percutaneous renal biopsy was performed during admission on both cases, showing severe glomerular and tubulointerstitial damages, in addition to typical type I MPGN findings such as mesangial cells and matrix interposition and subendothelial deposits. Because the continuous administration of steroid for more than 10 years did not ameliorate the clinical symptoms, steroid was markedly reduced or stopped in these cases. Such withdrawal from steroid therapy accelerated the amelioration of renal symptoms, including decrease in proteinuria, elevation of plasma protein and complement levels, and disappearance of generalized edema. The clinical courses of these cases indicate clinical choice of withdrawal from steroid therapy as one of the treatments in prolonged type I MPGN, which presents in childhood and shows steroid resistance.

BSC1 inhibition complements effects of vasopressin V2 receptor antagonist on hyponatremia in SIADH rats.

BACKGROUND: Severe hyponatremia is most frequently caused by the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Although the expressional alteration of the kidney-specific apical water channel, aquaporin 2 (AQP2), in the collecting duct has been demonstrated to be involved in the development of hyponatremia and the subsequent physiologic reaction that is resistant to arginine vasopressin (AVP; vasopressin escape) in SIADH, the complete pathogenesis of and the appropriate medical treatment for hyponatremia have yet to be elucidated. METHODS: Hyponatremia was induced in male Sprague-Dawley rats by water loading and subcutaneous infusion of 1-deamino-8-D-arginine vasopressin (dDAVP). For the treatment, a selective AVP V(2) receptor antagonist (OPC-31260) and/or a loop diuretic (furosemide) were administered orally. Protein expression of AQP2 and rat bumetanide-sensitive cotransporter (rBSC1) was examined by Western blotting during the hyponatremia and the subsequent treatment. RESULTS: We noted a markedly high expression of rBSC1 during the development of hyponatremia, and a relatively low expression during vasopressin escape. OPC-31260 administration elevated serum sodium level in a dose-dependent manner. The therapeutic effect, however, declined with increasing number of treatment days, and doses higher than 15 mg/kg/day induced severe toxicity. The physiologic parameters and the alterations of AQP2 and rBSC1 expression during the treatment demonstrated reactions that were completely opposite to those of vasopressin escape. Combination of a furosemide (100 mg/kg/day) and a low dose of OPC-31260 (5 mg/kg/day) additively elevated serum sodium level and sustained the elevated serum sodium level by significantly reducing sodium accumulation in the renal medulla. CONCLUSION: AVP-induced alterations of rBSC1 expression, as well as those of AQP2, are involved in the pathogenesis of SIADH. The pharmacologic blockade of AVP stimulus in SIADH limits its therapeutic efficacy by discontinuing the vasopressin escape, and the selective inhibition of rBSC1 complements this limitation.