Case series of four-factor prothrombin complex concentrate for warfarin reversal before heart transplantation.

OBJECTIVE: Describe the experience of using 4-factor prothrombin complex concentrate (PCC4) in patients with a ventricular assist device (VAD) scheduled for imminent heart transplant who are receiving warfarin. METHODS: We are reporting a clinical case series describing 4 patients with VADs treated with PCC4 for anticoagulation reversal before heart transplantation. Data collection was performed via retrospective medical chart review from March 27, 2014, to July 20, 2014. RESULTS: Average time to anticoagulation reversal was 2.45 hours and average volume of PCC4 injection was 86 mL. No patient experienced a thromboembolic event or a decrease in hemoglobin indicative of a bleeding event. Average volume of packed red blood cells, platelets, and fresh frozen plasma (FFP) patients received was 2,325 mL. Patient 1 experienced a hypersensitivity reaction and patient 2 experienced thrombocytopenia postoperatively. The average acquisition cost was $3,824 and the average retail price was $7,143 per complete dose. CONCLUSIONS: PCC4 contributed to efficient reduction of International Normalized Ratio (INR) before surgery. PCC4 requires less volume than FFP for similar INR reductions. PCC4 was a beneficial agent in our patients with VADs; however, a cost-benefit analysis is needed to evaluate the future utility of PCC4.

Genetic variant predicts bevacizumab-induced hypertension in ECOG-5103 and ECOG-2100.

BACKGROUND: Bevacizumab has broad anti-tumour activity, but substantial risk of hypertension. No reliable markers are available for predicting bevacizumab-induced hypertension. METHODS: A genome-wide association study (GWAS) was performed in the phase III bevacizumab-based adjuvant breast cancer trial, ECOG-5103, to evaluate for an association between genotypes and hypertension. GWAS was conducted in those who had experienced systolic blood pressure (SBP) >160 mm Hg during therapy using binary analysis and a cumulative dose model for the total exposure of bevacizumab. Common toxicity criteria (CTC) grade 3-5 hypertension was also assessed. Candidate SNP validation was performed in the randomised phase III trial, ECOG-2100. RESULTS: When using the phenotype of SBP>160 mm Hg, the most significant association in SV2C (rs6453204) approached and met genome-wide significance in the binary model (P=6.0 × 10(-8); OR=3.3) and in the cumulative dose model (P=4.7 × 10(-8); HR=2.2), respectively. Similar associations with rs6453204 were seen for CTC grade 3-5 hypertension but did not meet genome-wide significance. Validation study from ECOG-2100 demonstrated a statistically significant association between this SNP and grade 3/4 hypertension using the binary model (P-value=0.037; OR=2.4). CONCLUSIONS: A genetic variant in SV2C predicted clinically relevant bevacizumab-induced hypertension in two independent, randomised phase III trials.

Phosphorylation of Nedd4-2 by Sgk1 regulates epithelial Na(+) channel cell surface expression.

The epithelial Na(+) channel (ENaC) plays an essential role in the regulation of whole body Na(+) balance and blood pressure. The cell surface expression of this channel, a complex of three subunits (alpha, beta and gamma ENaC), has been shown to be regulated by hormones such as aldosterone and vasopressin and by intracellular signaling, including ubiquitylation and/or phosphorylation. However, the molecular mechanisms involving phosphorylation in the regulation of ENaC are unclear. Here we show by expression studies in Xenopus laevis oocytes that the aldosterone-induced Sgk1 kinase interacts with the ubiquitin protein ligase Nedd4-2 in a PY motif-dependent manner and phosphorylates Nedd4-2 on Ser444 and, to a lesser extent, Ser338. Such phosphorylation reduces the interaction between Nedd4-2 and ENaC, leading to elevated ENaC cell surface expression. These data show that phosphorylation of an enzyme involved in the ubiquitylation cascade (Nedd4-2) controls cell surface density of ENaC and propose a paradigm for the control of ion channels. Moreover, they suggest a novel and complete signaling cascade for aldosterone-dependent regulation of ENaC.

Blood pressure responses to small doses of amiloride and spironolactone in normotensive subjects.

The epithelial sodium channel (ENaC) is a principal site for sodium reabsorption and as such may participate importantly in blood pressure (BP) regulation. Amiloride, a direct inhibitor of ENaC, characteristically has mild antihypertensive properties, consistent with ENaC having more minor influences on BP regulation. Counter-regulatory influences may, however, prevent amiloride from effectively lowering BP. Aldosterone secretion is known to increase in response to the reduced sodium reabsorption that follows amiloride inhibition of ENaC, and because aldosterone upregulates ENaC function, we considered the possibility that secondary hyperaldosteronism mitigates the ability of amiloride to reduce BP. In the present study, the BP responses to amiloride (5 mg per day), spironolactone (25 mg per day), the combination of the 2 drugs, and placebo were studied in healthy normotensive subjects. Over 4 weeks of treatment, the combination of amiloride and spironolactone lowered systolic BP by 4.6+/-1.6 (mean+/-SEM) mm Hg (P=0.022) and diastolic BP by 2.2+/-1.2 mm Hg (P=0.30), whereas either drug alone had no significant effect on BP. The findings suggest that the 2 drugs with different modes of action-amiloride, a direct inhibitor of ENaC, and spironolactone, a mineralocorticoid receptor antagonist-may compliment each other's ability to inhibit ENaC and thereby reduce sodium reabsorption to a point at which BP decreases. On the other hand, we cannot rule out that the BP response resulted from the greater dose of total drug. The lowering of BP with small doses of inhibitors of ENaC serves as additional evidence for the importance of ENaC to the tonic maintenance of BP.

Antihypertensive efficacy and safety of losartan alone and in combination with hydrochlorothiazide in adult African Americans with mild to moderate hypertension.

BACKGROUND: African Americans with hypertension, particularly those with more severe blood pressure elevations, are generally less responsive to monotherapy from any antihypertensive class. These patients usually require treatment with drugs from > or = 2 antihypertensive classes to achieve adequate blood pressure control. OBJECTIVE: The purpose of this study was to assess the antihypertensive efficacy and safety of losartan alone and in combination with hydrochlorothiazide (HCTZ) in African American adults with mild to moderate hypertension. METHODS: In this 12-week, multicenter, double-blind, randomized, parallel-group, placebo-controlled study, African American patients were randomized in a 3:3:1 ratio to I of 3 treatment groups: placebo, losartan monotherapy (50 to 150 mg), or losartan plus HCTZ (50/0 to 50/12.5 to 100/25 mg). Doses were titrated at weeks 4 and 8 if sitting diastolic blood pressure (SiDBP) was > or = 90 mm Hg. Safety was assessed by determining the incidence of clinical and laboratory Adverse events and evaluating mean changes in pulse, body weight, electrocardiographic parameters, and laboratory test results. RESULTS: A total of 440 patients were randomized-188 to placebo, 193 to losartan monotherapy, and 59 to losartan/HCTZ; 391 completed the study. At week 12, the response rate with losartan monotherapy was 45.8%, with a significant (P < or = 0.01) lowering in mean SiDBP by 6.6 mm Hg compared with placebo; the response rate with placebo was 27.2%, with a mean SiDBP reduction of 3.9 mm Hg. Sitting systolic blood pressure (SiSBP) was significantly lowered with losartan monotherapy, by 6.4 mm Hg, compared with placebo (reduction of 2.3 mm Hg). The response rate with losartan/ HCTZ was 62.7%, with reductions in SiSBP and SiDBP of 16.8 mm Hg and 10.8 mm Hg, respectively (P < or = 0.01 vs placebo and losartan monotherapy). The incidence of clinical adverse events was comparable in the 3 treatment groups. CONCLUSIONS: The results of this study suggest that in African American patients, losartan monotherapy was significantly more effective than placebo in lowering SiSBP and SiDBP. Moreover, the losartan/ HCTZ combination regimen resulted in significant and clinically meaningful additional reductions in SiSBP and SiDBP compared with losartan monotherapy or placebo. Losartan monotherapy and the losartan/HCTZ regimens were generally as well tolerated as placebo.

Possible association but no linkage of the HSD11B2 gene encoding the kidney isozyme of 11beta-hydroxysteroid dehydrogenase to hypertension in Black people.

OBJECTIVE: The HSD11B2 (HSD11K) gene encoding the kidney isozyme of 11beta-hydroxysteroid dehydrogenase is mutated in the syndrome of apparent mineralocorticoid excess, an autosomal recessive form of salt-sensitive hypertension. This gene is thus a logical candidate locus for risk of essential hypertension. DESIGN AND METHODS: Because hypertension in Black people tends to be of the low-renin, salt sensitive type, we genotyped independent sets of hypertensives of Afro-American (59 kindreds) and Afro-Caribbean (66 kindreds) origin using a highly polymorphic (heterozygosity index 0.84) CA repeat polymorphism in the first intron of HSD11B2. Linkage was assessed by the affected pedigree member method. RESULTS: No linkage of hypertension to this locus could be demonstrated, but statistically significant allelic associations were noted. CONCLUSIONS: HSD11B2 does not have a strong influence on the development of essential hypertension in Black people, but weaker effects on blood pressure cannot be ruled out.

Rates of change in measures of body size vary by ethnicity and gender.

Obesity, a major risk factor for a variety of diseases, is more common in Blacks than in Whites. In the current study, a cohort of young Blacks and Whites was followed longitudinally to determine rates of change in body mass index (BMI) and subscapular and triceps skinfold thickness from the ages of 5 to 25 years. A significant difference in the rate of change of BMI (P<.0001) between Blacks and Whites was observed with Blacks gaining at a faster rate. The rate of increase of subscapular (P<.0001) and triceps fat (P<.0001) was significantly higher in the girls than in the boys. We also examined for differences by household income and maternal education level. Children from poorer families had more fat (P<.01 for all three outcomes), whereas education level was not related to the amount of body fat. Differences in the prevalence of obesity between Blacks and Whites and between males and females that manifest during adulthood appear to begin in childhood. The results re-emphasize the important need for early intervention in weight control measures.

Genetic determinants of homocysteine thiolactonase activity in humans: implications for atherosclerosis.

A metabolite of homocysteine (Hcy), the thioester Hcy thiolactone, damages proteins by modifying their lysine residues which may underlie Hcy-associated cardiovascular disease in humans. A protein component of high density lipoprotein, Hcy thiolactonase (HTase) hydrolyzes thiolactone to Hcy. Thiolactonase is a product of the polymorphic PON1 gene, also involved in detoxification of organophospates and implicated in cardiovascular disease. Polymorphism in PON1 affects the detoxifying activity of PON1 in a substrate-dependent manner. However, how PON1 polymorphism affects HTase activity is unknown. Here we report a strong association between the thiolactonase activity and PON1 genotype in human populations. High thiolactonase activity was associated with L55 and R192 alleles, more frequent in blacks than in whites. Low thiolactonase activity was associated with M55 and Q192 alleles, more frequent in whites than in blacks. High thiolactonase activity afforded better protection against protein homocysteinylation than low thiolactonase activity. These results suggest that variations in HTase may play a role in Hcy-associated cardiovascular disease.

Heart rate as a predictor of future blood pressure in schoolchildren.

Heart rate (HR) has been shown to predict future blood pressures (BP) in studies in adults. We explored the relation of HR to future BP levels in a cohort of 344 black and 456 white schoolchildren ages 5 to 19 years, to examine the hypothesis that HR predicts subsequent BP even very early in life. After making baseline measurements, BP was assessed longitudinally 1 to 24 additional times (mean = 8.25) after the baseline period, at intervals of approximately 6 months. We found that HR was significantly related to future diastolic BP in the black boys (P = .016) after adjusting for baseline diastolic BP, age, and body mass index, but not in the black girls or in the white children. Because HR is reflective of sympathetic nervous system (SNS) activity that in turn can be related to the renin-angiotensin system (RAS), we also explored the relation of HR to the RAS by studying relationships to variants in the angiotensinogen gene and the angiotensin I-converting enzyme (ACE) gene. We found a significantly positive relationship of HR to the presence of the deletion allele of the ACE gene (P = .0015), but, again, only in the black boys. Because blacks in general appear to retain additional sodium when compared with whites, the SNS, as reflected in the HR, may influence BP more when individuals have increased sodium retention. In summary, baseline HR predicted future diastolic BP in the black boys but not in the black girls or in the white children.

Molecular variations in the calcium-sensing receptor in relation to sodium balance and presence of hypertension in blacks and whites.

Sodium (Na) excretion is to an extent tied to calcium (Ca) excretion; increases in Ca result in increased Na excretion. We hypothesized that molecular variation in the calcium-sensing receptor (CaSR), which imparts certain of the influences of extracellular Ca, might be related to differences in Na balance and blood pressure. We further hypothesized that such an influence by CaSR is more pronounced in blacks than in whites, as the hypertension in blacks appears to be more dependent on Na retention. Three common molecular variants in CaSR were studied. Two were more frequent in the whites (A986S, P < .0001, and G990R, P = .093), whereas Q1011E was more frequent in the blacks (P < .0001). Two distinctly separate groups were studied: (1) healthy schoolchildren in whom levels of the renin-aldosterone axis and blood pressure were measured, and (2) normotensive and hypertensive adults. Studies of association were made separately in the whites and the blacks. No association of any of the variants with Na balance (as estimated from renin and aldosterone levels) was observed. In the black schoolchildren, Q1011E showed a marginal association with a higher blood pressure (P = .093 for systolic and P = .025 for diastolic), a relationship that was considered to be nonsignificant after adjusting for multiple comparisons. Nor was there a significant association of the variants with presence or absence of hypertension. In summary, studies of two cohorts that included whites and blacks did not suggest that molecular variations in the CaSR influence either Na balance or blood pressure.

Studies of renal injury III: lipid-induced nephropathy in type II diabetes.

UNLABELLED: Studies of renal injury III: Lipid-induced nephropathy in type II diabetes. BACKGROUND: Nephrotoxicity from elevated circulating lipids occurs in experimental and clinical situations. We tested the hypothesis that lipid-induced nephropathy causes advanced renal failure in rats with type II diabetes and dyslipidemia. METHODS: First generation (F1) hybrid rats derived from the spontaneous hypertensive heart failure rat (SHHF/Gmi-fa) and the LA/NIH-corpulent rat (LA/N-fa) were studied for 41 weeks while being on specific diets. Group 1 (14 rats) ingested 11.5% protein, 47.9% fat, and 40.6% carbohydrate. Group 2 (8 rats) ingested 26.9% protein, 16.7% animal fat, and 56.4% carbohydrate, and group 3 (20 rats) ingested 20.2% protein, 40.4% soy and coconut oil, and 39.4% carbohydrate. RESULTS: Hyperglycemia was more severe in rat groups 1 and 2 than in group 3. In contrast, circulating cholesterol and hydroperoxide levels were highest in group 3, intermediate in group 2, and lowest in group 1. Group 3 had severe renal failure secondary to glomerulosclerosis and tubulointerstitial disease, with striking deposition of the lipid peroxidation stress biomarker 4-hydroxynonenal in glomeruli and renal microvessels. Moreover, in group 3, increased arterial wall thickness also connoted vascular injury. In contrast, the glycoxidation stress biomarkers pentosidine and carboxymethyl-lysine were preferentially localized to renal tubules of hyperglycemic rats in groups 1 and 2 and did not segregate with the most severe renal injury. Glomerular and interstitial fibrosis was accompanied by proportional increases in renal transforming growth factor-beta1 levels, which were threefold higher in the hypercholesterolemic rats of group 3 than in the hyperglycemic rats of group 1. CONCLUSIONS: Acquisition of non-nodular glomerular sclerosis and tubulointerstitial disease is dependent on lipoxidation stress in rats with type II diabetes. On the other hand, in the absence of hypercholesterolemia, prolonged glycoxidation stress does not appear to be uniquely nephrotoxic.

Low-renin hypertension: more common than we think?

Low-renin hypertension is common and usually implies increased retention of sodium (Na(+)). In every case of known etiology, there is a mineralocorticoid-induced increase in number of epithelial Na(+) channels (ENaCs) in the collecting duct of the kidney, leading to a state of "hyperENaCactivity." In primary aldosteronism, a result of either an adrenal adenoma or bilateral adrenal hyperplasia, aldosterone itself mediates the increase in ENaC function. A severe form of low-renin hypertension in which a molecular mutation in ENaC prevents removal of the channel from the cell surface, known as Liddle's syndrome, results in increased net ENaC activity but, in this case, independently of an increase in aldosterone. Glucocorticoid remedial aldosteronism, an autosomal dominant form of primary aldosteronism, results from a "new" or chimeric gene for aldosterone synthase. Adrenocorticotropic hormone stimulates its expression as well as secretion of aldosterone. Apparent mineralocorticoid excess results from a molecular mutation that allows cortisol to bind to the mineralocorticoid receptor. Both glucocorticoid remedial aldosteronism and apparent mineralocorticoid excess result in an increase in the number of ENaCs. The question remains whether low-renin essential hypertension is related to an increase in ENaC activity. Low-renin hypertension is most common in black patients, who tend to have lower levels of aldosterone as well as renin, which are features that resemble those found in Liddle's syndrome. Preliminary findings suggest that black patients with low-renin hypertension who are resistant to standard antihypertensive therapy respond favorably to the addition of spironolactone, a mineralocorticoid receptor antagonist that reduces ENaC activity.

Absence of amiloride-sensitive sodium absorption in the airway of an infant with pseudohypoaldosteronism.

We report the measurement of transepithelial voltage across the nasal epithelium in a neonate with pseudohypoaldosteronism (PHA) type 1. A 5-day-old infant was seen with hyponatremia, hyperkalemia, and elevated plasma renin and aldosterone levels. Sweat Cl(-) concentration was also increased. Measurements of voltage showed a basal value of zero and the absence of an amiloride-sensitive voltage. However, voltage changed as expected for normal cyclic adenosine monophosphate-stimulated Cl(-) transport. These data demonstrate the absence of amiloride-sensitive Na(+) transport across airway epithelia in a neonate with PHA. The findings suggest that measurements of voltage could be of value in the diagnosis of PHA.

Functional analysis of a mutation occurring between the two in-frame AUG codons of human angiotensinogen.

Angiotensinogen (ANG) is the specific substrate of the renin-angiotensin system, a major participant in blood pressure control. We have identified a natural mutation at the -30 amino acid position of the angiotensinogen signal peptide, in which an arginine is replaced by a proline (R-30P). Heterozygous individuals with R-30P showed a tendency to lowered plasma angiotensinogen level (1563 ng of ANG I/ml (range 1129-1941)) compared with normal individuals in the family (1892 ng of ANG I/ml (range 1603-2072)). Human angiotensinogen mRNA has two in-phase translation initiation codons (AUG) starting upstream 39 and 66 nucleotides from the cap site. R-30P occurs in a cluster of basic residues adjacent to the first AUG codon that may affect intracellular sorting of the nascent protein. Pulse-chase experiments in transiently transfected cultured cells revealed that the R-30P mutation was associated with reduced amounts of both intra- and extracellular protein. In a cell-free system, we found that two forms of native angiotensinogen were generated by alternative initiation of translation at either AUG codon. Alteration of either the first or second AUG codons abolished the synthesis of the longer and the shorter form of native angiotensinogen, respectively. Furthermore, the rate of secretion of the shorter form was lower than that of the longer form. By transplanting angiotensinogen signal peptide onto green fluorescence protein, however, we found that both forms of the signal peptide could target green fluorescence protein, normally localized in the cytoplasm, to the secretory pathway. Although the R-30P mutation may not affect intracellular sorting of angiotensinogen in a qualitative manner, it leads to a quantitative reduction in the net secretion of mature angiotensinogen through decreased translocation or increased residence time in the endoplasmic reticulum.

Genetic variants in the epithelial sodium channel in relation to aldosterone and potassium excretion and risk for hypertension.

Renin and aldosterone secretion is often lower in blacks than in whites, characteristics that resemble a milder form of Liddle syndrome in which a mutation in the amiloride-sensitive epithelial sodium channel (ENaC) of the kidney results in enhanced resorption of sodium. In the present study, we looked for evidence that the intrinsic level of ENaC activity is indeed higher in blacks than in whites. In overnight urine samples collected from young people (249 white and 181 black subjects, mean age 13.4 years), the urinary aldosterone/potassium ratio, which is typically very low in Liddle syndrome, was lower in blacks than in whites: 0.421+/-0.024 (mean+/-SE) versus 0.582+/-0.016 nmol/mmol (P<0.0001). In addition, all but 1 of 5 molecular variants in ENaC were much more common in blacks than in whites. G442V in the beta-subunit, present in 16% of the blacks and in only 1 white, was associated with parameters reflective of a greater Na retention and potentially a higher ENaC activity: a lower plasma aldosterone concentration (P=0.070), a lower urinary aldosterone excretion rate (P=0.052), a higher potassium excretion rate (P=0.048), and a lower urinary aldosterone/potassium ratio (P=0.027). In a second cohort consisting of 126 black and 161 white normotensive subjects and 232 black and 188 white hypertensive subjects, betaG442V did not show a significant association with hypertension (P=0.089). On the other hand, a variant that was twice as common in whites, alphaT663A, was associated with being normotensive both in blacks (P=0.018) and in whites (P=0.034). Expression of either betaG442V or alphaT663A in Xenopus oocytes did not result in a change in basal Na current, consistent with the variants being in linkage disequilibrium with alleles at active loci. In conclusion, several lines of evidence are presented to suggest that ENaC activity is higher in blacks than in whites, which could contribute to racial differences in Na retention and the risk for hypertension.

Levels of mineralocorticoids in whites and blacks.

Blacks appear, on average, to retain more Na than whites. A higher production rate of mineralocorticoids could explain the greater Na retention in blacks. Although production of aldosterone has been shown to be lower in blacks, the level of another mineralocorticoid may be increased. Plasma levels of deoxycorticosterone and cortisol were measured in young whites (n=23; age=16.4+/-3.1[SD] years) and young blacks (n=25; age=13.8+/-1.3 years). Blacks had lower plasma levels of renin activity and aldosterone and lower urinary aldosterone excretion rates; thus, they appeared to be representative of blacks that retain additional Na. Plasma deoxycorticosterone levels were lower in blacks than in whites both at baseline (247+/-161 versus 381+/-270 pmol/L, P=0.048) and after stimulation with adrenocorticotropic hormone (822+/-294 versus 1127+/-628 pmol/L at 30 minutes, P=0.047; 925+/-366 versus 1440+/-834 pmol/L at 60 minutes, P=0.013). Cortisol levels were also lower in blacks at baseline (P=0.014) but were not significantly different from levels in whites after stimulation with adrenocorticotropic hormone. In a larger cohort of 407 whites (age=12.0+/-2.9 years) and 247 blacks (age=12.9+/-3.1 years), 18-hydroxycortisol excretion rates were also lower in blacks (P=0. 021). In conclusion, increased Na retention in blacks does not appear to be secondary to increased production of either aldosterone, deoxycorticosterone, cortisol, or 18-hydroxycortisol. A primary renal mechanism may mediate the increase in Na reabsorption in blacks.

Do maritime crew members have sleep disturbances?

Data obtained from surveys of two samples of maritime crew members were studied for differences in self-reported sleep lengths and sleep problems. The data addressed both on- and off-duty variables. Statistical analysis of the data found that on-duty sleep length was shorter than off-duty sleep length for both groups. The two groups' responses to various sleep-problem items were significantly different. Most responses were below the scale mid-point. The differences between on- and off-duty sleep-problem items were not significant. Following a factor analysis, selected sleep-problem items were combined to form a composite Sleep Disturbance Scale. Using this composite measure, the correlation between the composite and sleep length was not significant. Overall, the results indicate that caution should be exercised before labeling shift workers as having "disturbed sleep" or suffering from "sleep disorders." The results do confirm the previous findings that shiftwork reduces sleep length on workdays.

Defective regulation of the epithelial Na+ channel by Nedd4 in Liddle's syndrome.

Liddle's syndrome is an inherited form of hypertension linked to mutations in the epithelial Na+ channel (ENaC). ENaC is composed of three subunits (alpha, beta, gamma), each containing a COOH-terminal PY motif (xPPxY). Mutations causing Liddle's syndrome alter or delete the PY motifs of beta- or gamma-ENaC. We recently demonstrated that the ubiquitin-protein ligase Nedd4 binds these PY motifs and that ENaC is regulated by ubiquitination. Here, we investigate, using the Xenopus oocyte system, whether Nedd4 affects ENaC function. Overexpression of wild-type Nedd4, together with ENaC, inhibited channel activity, whereas a catalytically inactive Nedd4 stimulated it, likely by acting as a competitive antagonist to endogenous Nedd4. These effects were dependant on the PY motifs, because no Nedd4-mediated changes in channel activity were observed in ENaC lacking them. The effect of Nedd4 on ENaC missing only one PY motif (of beta-ENaC), as originally described in patients with Liddle's syndrome, was intermediate. Changes were due entirely to alterations in ENaC numbers at the plasma membrane, as determined by surface binding and immunofluorescence. Our results demonstrate that Nedd4 is a negative regulator of ENaC and suggest that the loss of Nedd4 binding sites in ENaC observed in Liddle's syndrome may explain the increase in channel number at the cell surface, increased Na+ reabsorption by the distal nephron, and hence the hypertension.

Serum angiotensinogen concentration in relation to gonadal hormones, body size, and genotype in growing young people.

Multiple factors are thought to influence the level of circulating angiotensinogen (AGT). We showed previously that the serum AGT concentration was significantly related to body mass index (BMI) in a cohort of young people. In the present study, we studied whether levels of the gonadal hormones estradiol and testosterone might also predict the AGT level and might contribute to the BMI effect, since both the production of these hormones and BMI increase with age. In boys (n=127; mean+/-SD age, 14.7+/-1.9 years) and girls (n=104; age, 14.8+/-1.9 years) studied as a single group, we found a significant association of AGT level with level of estradiol (P=0.015) after adjustment for haplotype, age, race, testosterone concentration, and BMI. In girls studied alone, the level of AGT showed a significantly positive relation to level of testosterone (P=0.043), possibly a result of peripheral conversion of testosterone to estradiol, after adjustment for haplotype, age, race, estradiol concentration, and BMI. In boys, on the other hand, the level of testosterone was inversely related to AGT concentration (P=0.019), again after making adjustments for the other variables. Finally, in pairs of subjects matched for BMI, age, race, and gender where 1 member of each pair had either 1 or 2 copies of an AGT gene haplotype (T235 and -1074t) and the other member had no copy, the level of AGT was higher in the carrier of a haplotype in 24 of the 34 pairs (P<0.001). In conclusion, gonadal hormones are an additional influence on the circulating level of AGT in growing young people. In addition, with matching for BMI and other covariates, there is a strong association of AGT genotype with the serum level of AGT, emphasizing the importance of AGT gene expression as a determinant of the circulating level of AGT.