MicroRNA-130a represses transcriptional activity of aquaporin 4 M1 promoter.

Aquaporins (AQPs) are transmembrane water channels ubiquitously expressed in mammalian tissues. They play prominent roles in maintaining cellular fluid balance. Although expression of AQP1, -3, -4, -5, -8, -9, and -11 has been reported in the central nervous system, it is AQP4 that is predominately expressed. Its importance in fluid regulation in cerebral edema conditions has been highlighted in several studies, and we have also shown that translational regulation of AQP4 by miR-320a could prove to be useful in infarct volume reduction in middle cerebral artery occluded rat brain. There is evidence for the existence of two AQP4 transcripts (M1 and M23) in the brain arising from two alternative promoters. Because the AQP4 M1 isoform exhibits greater water permeability, in this study, we explored the possibility of microRNA-based transcriptional regulation of the AQP4 M1 promoter. Using RegRNA software, we identified 34 microRNAs predicted to target the AQP4 M1 promoter region. MicroRNA profiling, quantitative stem-loop PCR, and luciferase reporter assays revealed that miR-130a, -152, -668, -939, and -1280, which were highly expressed in astrocytes, could regulate the promoter activity. Of these, miR-130a was identified as a strong transcriptional repressor of the AQP4 M1 isoform. In vivo studies revealed that LNA(TM) anti-miR-130a could up-regulate the AQP4 M1 transcript and its protein to bring about a reduction in cerebral infarct and promote recovery.

Riboregulators in kidney development and function.

The discovery of microRNAs has brought in another level of intricacy in gene regulation. These microRNAs are small non-coding RNAs that have dual ability to act as repressors or inducers of gene activity. MicroRNAs have been implicated in a wide spectrum of biological processes and their expressions have been found to be dysregulated in several diseases. Recently, microRNAs have emerged as a new area of interest in renal development and pathology. MicroRNA profilings have revealed a number of microRNAs that are specific to the kidney or restricted to certain regions of the organ suggesting possible exclusive roles therein. Recently, knockout studies have shown that these riboregulators are critical for normal renal growth and functional renal system. Individual microRNAs have also been identified in renal disease models including kidney cancers, diabetic nephropathy and polycystic kidney disease. Several mechanisms of modulating microRNA activity have also been introduced in recent years. Further progress in the understanding of microRNA activity, identification of microRNA signatures in different states as well as advancement of microRNA manipulation techniques will be valuable for kidney research.

Aquaporins and fetal fluid balance.

Aquaporins were first described as channels which increased permeability of lipid membranes to water, in response to osmotic and/or hydrostatic gradients. Some were shown to increase permeability also of other small solutes, particularly urea and glycerol. More recently other functions have been attributed to some, such as involvement in angiogenesis, cell migration, and adhesion. All of these processes are essential to the establishment and maintenance of a healthy placenta, fetus, fetal membranes and fluids. So far aquaporins have been found in the placenta and fetal membranes [AQPs1,3,4,5,8,9] and in organs producing fluid into the amniotic compartment [lung 1,3,4,5; kidney 1,2,3,4], and it is postulated that these aquaporins may function in all of the above roles in these organs. It is proposed the ontogeny of aquaporin expression in a species (sheep) in which lung and kidney mature in comparable fashion to the maturation of these organs in human are more relevant to the understanding of the potential importance of these channels in the human than studies in the short-gestation, relatively immature young of the rodents.

Factors influencing mammalian kidney development: implications for health in adult life.

There are many reasons why it is timely to review the development of the mammalian kidney. Perhaps the most important of these is the increasing amount of evidence to demonstrate that factors which impinge on/alter the normal developmental processes of this organ can have lifelong consequences for the health of the adult. The'Developmental Origins of Health and Adult Disease' (DOHaD) hypothesis, proposes that changes in the environment during the development of an organ or system, can have permanent deleterious effects leading to increased risk of cardiovascular and/or metabolic disease. The permanent metanephric kidney has been shown to be very vulnerable to such influences with many factors shown to alter both the permanent structure and the level of expression of important functional genes. Thus it is important to understand the precise timing of kidney development in terms of both structure and the genes involved at each stage. Such knowledge has been gained by significant advances in technology, which allow quantification of the number of nephrons by unbiased stereology, detections of both levels and site of gene expression,'knock-out' and knock-in' of genes in animal (mainly mouse) models and by the ability to examine nephron development, in real time, in culture systems.

Maternal exposure to dexamethasone or cortisol in early pregnancy differentially alters insulin secretion and glucose homeostasis in adult male sheep offspring.

An adverse intrauterine environment increases the risk of developing various adult-onset diseases, whose nature varies with the timing of exposure. Maternal undernutrition in humans can increase adiposity, and the risk of coronary heart disease and impaired glucose tolerance in adult life, which may be partly mediated by maternal or fetal endocrine stress responses. In sheep, dexamethasone in early pregnancy impairs cardiovascular function, but not glucose homeostasis in adult female offspring. However, male offspring are often more susceptible to early life "programming". Pregnant sheep were infused intravenously with saline (0.19 ml/h), dexamethasone (0.48 mg/h), or cortisol (5 mg/h), for 2 days from 26 to 28 days of gestation. In male offspring, size at birth and postnatal growth were measured, and glucose tolerance [intravenous glucose tolerance test (IVGTT)], insulin secretion, and insulin sensitivity of glucose, alpha-amino nitrogen, and free fatty acid metabolism were assessed at 4 yr of age. We show that cortisol, but not dexamethasone, treatment of mothers causes fasting hyperglycemia in adult male offspring. Maternal cortisol induced a second-phase hyperinsulinemia during IVGTT, whereas maternal dexamethasone induced a first-phase hyperinsulinemia. Dexamethasone improved glucose tolerance, while cortisol had no impact, and neither affected insulin sensitivity. This suggests that maternal glucocorticoid exposure in early pregnancy alters glucose homeostasis and induces hyperinsulinemia in adult male offspring, but in a glucocorticoid-specific manner. These consequences of glucocorticoid exposure in early pregnancy may lead to pancreatic exhaustion and diabetes longer term and are consistent with stress during early pregnancy contributing to such outcomes in humans.

Sex differences in postnatal growth and renal development in offspring of rabbit mothers with chronic secondary hypertension.

Previously, we demonstrated that adult blood pressure was increased in offspring of rabbit mothers with chronic secondary renal hypertension. Our study identified sex-specific differences in the programming of hypertension, with female, not male, offspring, having increased blood pressure at 30 wk of age. The aim of this study was to characterize the maternal hypertension during pregnancy to determine potential programming stimuli. Further, we examined the impact of chronic maternal hypertension on offspring birth weight, nephron number, and renal noradrenaline content (as an index of renal innervation density). Three groups of mothers and their offspring were studied: two-kidney, one-wrap (2K-1W, n = 9 mothers) hypertensive, two-kidney, two-wrap (2K-2W, n = 8) hypertensive, and a sham-operated group (n = 9). Mean arterial blood pressure was increased by approximately 20 mmHg throughout pregnancy in both hypertensive groups compared with sham mothers (P(G) < 0.001). Plasma renin activity (PRA; P(G) < 0.05) and aldosterone (P(G) < 0.05) levels were increased during gestation in the 2K-1W, but not the 2K-2W mothers. Birth weight was increased by approximately 20% in offspring of both groups of hypertensive mothers (P(T) < 0.001), though this was associated with a reduction in litter size. Renal noradrenaline content was increased ( approximately 40%, P < 0.05) at 5 wk of age in female 2K-1W offspring compared with sham offspring. Glomerular number was not reduced in female offspring of either group of hypertensive mothers; however, glomerular tuft volume was reduced in female 2K-2W offspring (P < 0.05), indicative of a reduction in glomerular filtration surface area. In conclusion, the two models of renal hypertension produced differential effects on the offspring. The impact of a stimulated maternal renin-angiotensin system in the 2K-1W model of hypertension may influence development of the renal sympathetic nerves and contribute to programming of adult hypertension.

Differential effects of prenatal exposure to dexamethasone or cortisol on circulatory control mechanisms mediated by angiotensin II in the central nervous system of adult sheep.

Prenatal exposure to elevated maternal glucocorticoids (dexamethasone (DEX) or cortisol (CORT)) for 2 days early in pregnancy can 'programme' alterations in adult offspring of sheep, including elevated arterial pressure. DEX treatment also results in greater angiotensin II type 1 (AT1) receptor expression in the medulla oblongata in late gestation fetuses than in saline (SAL)- or CORT-exposed animals. We hypothesized that this would result in functional changes in brainstem angiotensinergic control of cardiovascular function in DEX- but not CORT-exposed animals. To test this hypothesis, cardiovascular responses to intracerebroventricular (I.C.V.) angiotensin II were examined in adult male offspring exposed to DEX (0.48 mg h(-1); n = 7), CORT (5 mg h(-1), n = 6) or SAL (n = 9) from 26 to 28 days of gestation. Increases in mean arterial pressure during i.c.v. infusion of angiotensin II (1 or 10 microg h(-1)) were significantly greater in the DEX group (10 +/- 1 mmHg at 1 microg h(-1)) compared with SAL (6 +/- 1 mmHg) or CORT (6 +/- 1 mmHg) animals (P < 0.05). I.C.V. infusion of the AT1 antagonist losartan significantly decreased cardiac output and heart rate in DEX animals, but not in SAL or CORT animals. Thus, increased expression of brainstem AT1 receptor mRNA after prenatal DEX is associated with increased responsiveness of cardiovascular control to activation of brain AT receptors by exogenous and endogenous angiotensin II. The altered role of the brain RAS in sheep exposed prenatally to DEX was not observed in sheep exposed prenatally to cortisol, suggesting these two glucocorticoids have distinct programming actions.

Quantitative comparison of placental expression of three aquaporin genes.

Three water channel proteins, aquaporins, have been shown to be expressed in the placentae of humans and sheep-AQP1, 3, 8; AQP1 is in the vasculature, whereas AQP3, 8 are in the trophoblast cells. In this study we used the sensitive and reproducible technique of real-time PCR to compare the level of expression of the mRNAs for AQP1, 3 and 8 in the ovine placenta at five stages of gestation (27, 45, 66, 100 and 140 days-where term approximately 150 days). AQP3 was quantitatively the most highly expressed AQP at 66, 100, and 140 days). At 27 days before significant trophoblast development had occurred, the only AQP present was AQP1, in the vasculature. The expression of these aquaporins underlie the high water and urea permeability of the ovine placenta in the last half of pregnancy.

Prolonged low-dose dexamethasone treatment, in early gestation, does not alter blood pressure or renal function in adult sheep.

Low-dose dexamethasone treatment is used in pregnancies where the fetus is suspected to be at risk of congenital adrenal hyperplasia (CAH). In order to see if such treatment had long-term effects, pregnant ewes were treated with dexamethasone (20 micro g/kg maternal body weight) or saline from 25 to 45 days of gestation and blood pressure and renal function studied in offspring at 2 Years of age. There were 11 animals from dexamethasone treatment (six females and five males) and nine lambs from saline treatment (five females and four males). We aimed to study blood pressure and heart rate in the adult animals of both genders, and renal function only in the adult female animals. In both females and males, blood pressure and heart rate were similar between the two groups of animals. The excretion rates of sodium and potassium were similar between the two groups of animals. In addition, glomerular filtration rate was not different between the two groups of animals (112+/-11 ml/kg per h (S.E.M.) in saline-treated females vs 112+/-10 ml/kg per h in dexamethasone-treated females). There were no differences in body weight or weights of the kidney and heart between the treatments in both females and males. In conclusion, these results are reassuring for patients similarly exposed to prenatal dexamethasone treatment for CAH, as in our animal model no evidence of altered renal function or predisposition to adult hypertension was found.

Programming the cardiovascular system, kidney and the brain--a review.

The concept that 'life before birth' or the 'first environment' is important in determining subsequent risk for the development of cardiovascular/metabolic disease is now gaining acceptance. There are substantial data from animal experiments that complement and enhance the epidemiological data from human studies. We argue that any factor which disrupts nephrogenesis, and lowers nephron number, during the period of active nephrogenesis, will induce malapadaptive changes in the future functioning of that kidney and predispose to the onset of adult hypertension. Such factors include exposure of the mother, to a particular low-protein diet, excess synthetic or natural glucocorticoid at certain critical periods, mild vitamin A deficiency, elevated blood glucose, unilateral nephrectomy during the period of nephrogenesis, as well as the deletion of one allele of a gene (GDNF) involved in normal metanephric development. All of these stresses are associated with a reduction (20-40 per cent) in total nephron number in the adult, and the development of hypertension. In some hypertensive models, (rats) there is evidence of alterations in the components of the hippocampal/hypothalamic/pituitary/adrenal axis, whereas in others (sheep) there are alterations in the expression of angiotensinogen (hypothalamus) and angiotensin II receptor type I (AT(1)) in the medulla oblongata. The surprising finding is that the period when the kidney and brain are most vulnerable is very early in development, when both organs are in an extremely primitive state of development.

Aquaporin gene expression and regulation in the ovine fetal lung.

Fetal lung development is dependent upon secretion of liquid into the future airways which must be cleared at birth to establish air-breathing. Aquaporins (AQP) 1, 3, 4 and 5 are membranous water channel proteins that are present in the lung after birth in rodents, with little expression before birth. Our aim was to describe the changes in AQP1, 3, 4 and 5 expression and protein levels in the fetal lung of a long-gestation species (sheep) and in response to physiological factors known to alter fetal lung liquid dynamics. Both mRNA and high protein levels were detected for AQP1, 3, 4 and 5 by day 100 (term is ~150 days in ovine fetuses). A cortisol infusion (120-131 days) significantly (P < 0.05) increased AQP1 (0.9 +/- 0.2 (n = 4) vs.1.8 +/- 0.3 (n = 5)) and AQP5 (8.8 +/- 0.6 vs. 14.1 +/- 1.2) mRNA levels in fetal lung (measured by real-time PCR). Ten days of tracheal obstruction significantly (P < 0.05) decreased AQP5 mRNA levels (6.1 +/- 0.9 (n = 5) vs. 2.7 +/- 0.3 (n = 5)). Immunohistochemistry was used to show that protein levels changed in parallel with the mRNA changes. These findings suggest that AQPs could be involved in lung liquid production and reabsorption during fetal development in long-gestation species.

Reduced nephron number in adult sheep, hypertensive as a result of prenatal glucocorticoid treatment.

There is some evidence, mainly from rodent studies, that any factor which alters the final total number of nephrons formed, during nephrogenesis, will result in hypertension in adult life. Sheep, programmed to become hypertensive by exposure to synthetic glucocorticoid (dexamethasone, 0.48 mg h-1, for 48 h) early in development (~27 days of gestation), were killed at 7 years of age, and had nephron counting performed by unbiased stereology. Mean arterial pressure was 83 +/- 4 mmHg in the dexamethasone (DEX) group (n = 5), and 73 +/- 5 in the control (CON; n = 7; P < 0.05). The total nephron number, in the right kidney (249 070 +/- 14 331; n = 5) was significantly lower (P < 0.01) than that of controls (402 787 +/- 30 458; n = 7). Mean glomerular volume was larger in the DEX than the CON group (P < 0.01), but there was no significant difference in the sclerosis index between the two groups. Low nephron number was associated with grossly enlarged and dilated proximal tubules and greater accumulation of collagen type I and type III in the tubular interstitium and periadventitia of the renal cortical vessels. These data suggest that the hypertensive programming effect of glucocorticoid treatment, early in kidney development, results, at least in part, from impaired nephrogenesis.

Prenatal exposure to glucocorticoids and adult disease.

There is evidence to suggest that an individual's susceptibility to cardiovascular disease cannot be entirely explained by differences in life style factors (i.e., low physical activity, high fat/salt diet), or genetic causes, but may also be influenced by factors encountered during intrauterine life. Epidemiological studies found the link between low birth weight for gestational age (a broad index of sub-optimal intrauterine environment) and increased incidence of cardiovascular and metabolic diseases in adulthood. Many animal models in which the intrauterine environment was altered during early/late or throughout gestation demonstrated long-term effects on adult health. In general stress in early gestation is more likely to be associated with adult cardiovascular disease including hypertension, whereas late gestation stress may also be associated with adult hypotension in addition to metabolic/endocrine abnormalities. Two systems have been widely hypothesised to serve as mechanisms via which adverse prenatal influences impinge on adult cardiovascular and metabolic disease; hippocampal-hypothalamo-pituitary-adrenal axis (HHPA) and renin-angiotensin system (RAS). Interestingly, at least in our animal model of adult hypertension after brief/early prenatal glucocorticoid exposure, HHPA axis is not altered when studied either in late gestation or at several stages during adulthood. However, our more recent results, using the same animal model, suggest a major role for the central and renal RAS. This review will mainly focus on animal models and potential mechanisms via which a perturbed intrauterine environment (undernutrition or steroid exposure) lead to adult cardiovascular and/or metabolic disease.

Maternal glucocorticoid treatment programs alterations in the renin-angiotensin system of the ovine fetal kidney.

Ovine fetuses exposed to high concentrations of synthetic (dexamethasone, D) or naturally occurring glucocorticoids (cortisol, F) in utero during early gestation develop high blood pressure in adulthood. To investigate potential mechanisms involved, we examined the role of the renal renin-angiotensin system (RAS). Ewes were infused with isotonic saline (S, n = 11), D (n = 12, 0.48 mg/h), or F (n = 5, 5 mg/h) for 48 h between d 26 and 28 of gestation (term = 150 d). Ewes carrying twins (S, n = 5; D, n = 6; F, n = 5) were killed at 130 d of gestation. The mRNA levels for angiotensinogen, the AT(1) receptor and AT(2) receptor, were increased in the fetal kidneys after D treatment. Prenatal infusions of F produced similar effects on the AT(1) receptor. Single fetuses (S, n = 6; D, n = 6) were cannulated and infused with angiotensin II for 3 d beginning at 127 d of gestation. Basal blood pressure was similar in both groups and increased similarly with angiotensin II infusion. However, increases in urine flow and glomerular filtration rate were significantly reduced and kidney weights increased in the D-treated group. These results indicate that treatment with D very early in gestation causes significant alterations in the RAS in the fetal kidney 100 d later with functional consequences. Changes in the RAS in the developing kidney may be an important mechanism in the development of adult disease.

Prolonged low-dose dexamethasone, in early gestation, has no long-term deleterious effect on normal ovine fetuses.

Low-dose dexamethasone (D) treatment is used in pregnancies where the fetus is suspected to be at risk of congenital/virilizing adrenal hyperplasia. To study if this treatment had any immediate or long-term effects in normal fetuses, pregnant ewes were treated with D (20 microg/kg maternal body weight x d) or saline (S), from d 25-45 of gestation. Tissue was collected from fetuses killed at 45 d (S = 6; D = 8), 130 d (S = 8; D = 8), or lambs at 2 months of age (S = 6; D = 6) and mRNA levels measured using real-time PCR. D treatment reduced adrenal wt at 45 d (S, 12.2 +/- 0.7 mg; D, 6.3 +/- 0.4 mg) and significantly decreased adrenal mRNA for P(450scc). At 130 d, fetuses from the D treatment were growth retarded (S, 3.2 +/- 0.1 kg; D, 2.5 +/- 0.1 g), but the adrenals were appropriate for the body weight. mRNA levels of angiotensinogen, the AT(1) receptor and mineralocorticoid receptor (MR) and GR were similar in kidney and brain (hypothalamus, hippocampus, medulla oblongata) except for hippocampal expression of MR and GR, which was significantly decreased by D treatment. By 2 months, BW and hippocampal MR and GR mRNA levels were similar, and lambs were normotensive (S, 83 +/- 3 mm Hg; D, 78 +/- 3 mm Hg). Thus, there were no persistent, long-term effects of prolonged low-dose D treatment in normal ovine fetuses.

Blood pressure, heart rate, hormonal and other acute responses to rubber-ring castration and tail docking of lambs.

AIM: To examine cardiovascular, hormonal and other physiological responses of 2-month-old lambs to rubber-ring castration and tail docking. METHODS: Twenty-two male lambs, well accustomed to handling and prepared with femoral artery and jugular vein cannulae, were studied during a 5 h control period and, at least 2 days later, for 1 h before and 4 h after castration and tail docking using rubber rings. Pressure recordings were made via femoral cannulae and blood samples for analysis of plasma constituents were taken from jugular cannulae. RESULTS: Mean systolic, diastolic and mean arterial blood pressure, heart rate and the plasma concentrations of adrenocorticotropic hormone (ACTH) and cortisol all increased markedly during the first 1 h after ring castration and tail docking. Although plasma ACTH and cortisol concentrations had returned to control levels by 2.5-3 h, blood pressures and heart rate were still elevated 4 h after ring application. In contrast, there were no significant changes in mean plasma concentrations of renin, electrolytes, minerals, glucose, lactate, urea, creatinine, total carbon dioxide and total proteins, plasma osmolality or the haematocrit after ring application. There were no significant changes in the mean values for any parameter during the 5 h control period or the 1 h period before ring application. CONCLUSION: Systolic, diastolic and mean arterial blood pressure and heart rate may be more sensitive than plasma ACTH or cortisol concentrations as indices of low-grade pain induced by ring castration and tail docking. Alternatively, it is possible that by 4 h after ring placement a small shift in sympathetic tone still persists in the absence of low-grade pain.

Organs/systems potentially involved in one model of programmed hypertension in sheep.

1. When pregnant ewes and their fetuses are exposed to the synthetic glucocorticoid dexamethasone for 2 days early in pregnancy (days 26-28; term 145-150 days), female offspring have increased blood pressure relative to a control group. In one series, this was shown to be due to increased cardiac output, concomitant with a reset mean arterial pressure/heart rate reflex. The first group of such animals had, by the age of 7 years, left ventricular hypertrophy and reduced cardiac functional capacity. 2. The elevation in blood pressure is not maintained by any change in the peripheral renin-angiotensin system (RAS). 3. There is, however, preliminary evidence that some aspects of local RAS (particularly in the kidney and brain) could have participated in the 'programming' event. The levels of mRNA for angiotensin II receptors (AT1, AT2) and angiotensinogen are increased in the kidney of such dexamethasone-treated fetuses in late gestation (130 days), some 100 days after steroid treatment. Similar increases in AT1 mRNA in the medulla oblongata of the fetal brain and large increases of mRNA for angiotensinogen occur in the hypothalamus. 4. These findings, together with evidence from the literature, suggest that both the kidney and parts of the brain are affected by events that also 'program' high blood pressure in the offspring of animals in which the intra-uterine environment has been perturbed at some stage.

Impaired cardiac functional reserve and left ventricular hypertrophy in adult sheep after prenatal dexamethasone exposure.

We have shown that exposure of pregnant ewes to dexamethasone (11.5 mg/d for 2 days) at 27 days of gestation (term, 150 days) led to increased blood pressure and cardiac output in adult offspring. In this study, we hypothesized that dexamethasone-induced hypertension is associated with left ventricular hypertrophy and a reduced cardiac functional reserve (CO(max-0)). Six control animals (group C) and five dexamethasone-exposed animals (group D) were volume-loaded with Hemaccel until the wedge pressure was 13 mm Hg (baseline). The wedge pressure was held constant during an infusion of dobutamine at incremental doses (0.4 to 12 microgram/kg/min) while blood pressure and cardiac output were measured. The same protocol was repeated in each animal 5 days later under mild general anesthesia (1.5% isoflurane), when transthoracic echocardiography (M-mode) was obtained. Group D showed a reduced CO(max-0) in response to dobutamine during both conscious (89+/-22 versus 150+/-25 mL/kg/min in control; P<0.01) and anesthetized states (91+/-38 versus 156+/-56 mL/kg/min in control; P<0.05). Reduced CO(max-0) in group D was associated with higher left ventricular mass index compared with group C (2.6+/-0.67 versus 1.8+/-0.51 g/kg; P<0.05). In addition, group D showed a reduced cardiac contractility reserve (FS(max-0)) in response to dobutamine (21+/-22% versus 54+/-34% in group C; P<0.05). An impaired cardiac functional reserve in group D was associated with increased left ventricular type I collagen content. In conclusion, brief prenatal exposure to dexamethasone led to the development of hypertension, left ventricular hypertrophy, and reduced cardiac functional reserve in adult life.

Local inhibition of nitric oxide temporarily stimulates aldosterone secretion in conscious sheep in vivo.

The effect of localized blockage of endogenous nitric oxide (NO) on basal aldosterone secretion was studied in conscious sheep with autotransplanted adrenal glands. We have shown that infusion of the NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 130 microg/l blood flow) significantly stimulated basal aldosterone secretion rate (ASR). This stimulatory effect was seen up to 4 h of infusion. Beyond this time point, however, the elevated ASR level was not sustained, and it was seen to drop markedly to lower than control values at 5 h. L-NAME had no effect on cortisol secretion rate (FSR) during the first 4 h of infusion, but a significant reduction in FSR was seen by the 8-h time point. Adrenal blood flow was consistently decreased in association with long L-NAME infusion. Additionally, L-NAME was shown to have no effect on aldosterone secretion when infused systemically. We conclude that the relationship between NO and aldosterone secretion is an inhibitory one, in which NO seems to have a negative effect on basal aldosterone secretion.

The peripheral renin-angiotensin system is not involved in the hypertension of sheep exposed to prenatal dexamethasone.

1. Fetal exposure to an adverse intrauterine environment has been linked with cardiovascular and metabolic disease later in life. We have shown previously, in sheep, that brief exposure (48 h) to maternally administered dexamethasone (0.28 mg/kg per day) at 27 days of gestation (prenatal treatment group (PTG) 1; term approximately 150 days), but not at 64 days of gestation (PTG2), produced hypertensive offspring at 40 months of age. The present study aimed to determine whether the elevated blood pressure in these sheep was associated with an altered peripheral renin-angiotensin system (RAS). 2. Measurements of the basal levels of the RAS components (renin, angiotensinogen, angiotensin (Ang) I, angiotensin- converting enzyme (ACE), AngII and Ang-(1-7)) were made. In addition, we studied the effect of a peripherally administered AngII type 1 (AT1) receptor antagonist (irbesartan at 1.02 mg/kg per h) on mean arterial pressure (MAP) over 4.5 h. 3. There was no significant difference in basal plasma concentrations of the components of the RAS measured between control (n = 7) and PTG1 (n = 5) or PTG2 (n = 6) animals. The MAP in PTG1 was significantly higher than in the control group during both vehicle infusion and AT1 receptor blockade. The effect of 4.5 h irbesartan (1.02 mg/kg per h) infusion on blood pressure was similar between the groups. 4. In conclusion, intrauterine exposure for 48 h to maternally administered dexamethasone at 27 days of gestation caused elevated blood pressure in adult sheep that does not appear to be associated with an alteration in the peripheral RAS.