Losartan blocks aldosterone and renal vascular responses to angiotensin II in humans

In vitro and animal studies have demonstrated that the effect of angiotensin II (Ang II) on aldosterone is mediated through the Ang II type 1 receptor. However, it has been difficult to demonstrate an effect of Ang II type 1 receptor blockade on aldosterone levels in human studies. One possible explanation is that subjects have not been studied under salt-controlled conditions. Therefore, we examined the effects of losartan on the aldosterone and renal plasma flow responses to Ang II infusion in six normotensive subjects under low and high salt conditions. Ang II was infused in graded doses (0.3 to 10 ng/kg per minute) in the presence and absence of losartan (a single 50-mg oral dose). Renal plasma flow was assessed by measurement of para-aminohippurate clearance. Blood pressure, plasma aldosterone levels (low salt conditions only), and para-aminohippurate clearance were measured before and after each Ang II dose. Losartan had no effect on baseline systolic pressure but attenuated the systolic pressure response to exogenous Ang II during both low salt (0.7 +/- 1.9 versus 6.7 +/- 1.4 mm Hg, P = .001) and high salt (2.0 +/- 1.9 versus 12.3 +/- 2.1 mm Hg, P = .006) conditions. Under low salt conditions, losartan reduced the baseline plasma aldosterone level from 1135 +/- 204 to 558 +/- 102 pmol/L (P = .015) and blocked the aldosterone response to Ang II (-49 +/- 110 versus +436 +/- 83 pmol/L, P = .019). During high salt conditions, losartan had no effect on baseline renal plasma flow but attenuated the renal plasma flow response to Ang II (-90.1 +/- 15.1 versus -185.1 +/- 2.6 mL/min per 1.73 m2, P = .013). These data confirm that losartan lowers both basal and exogenous Ang II-stimulated aldosterone levels under low salt conditions. Losartan does not significantly affect baseline renal plasma flow but does attenuate the renal plasma flow response to exogenous Ang II under high salt conditions.     

Deferential roles of angiotensin receptor subtypes in adrenocortical function in mice

The functional significance of angiotensin II (Ang II) receptor subtypes in adrenals remains unknown. Ang II receptor type 1a (AT1a) expression was localized by in situ hybridization to the zona glomerulosa and zona fasciculata, while AT1b was localized to the zona glomerulosa. Plasma aldosterone and corticosterone levels were measured after injection with Ang II or the type 2 receptor (AT2) agonist CGP-42112 in wild-type and AT1a deficient mice. Aldosterone and corticosterone levels were lower in AT1a deficient mice. Ang II increased plasma aldosterone levels in AT1a deficient mice, but to a lesser extent in mice pretreated with nonselective AT1a/AT1b antagonist, CV-11974. CGP-42112 did not affect aldosterone levels. Ang II increased corticosterone levels in wild-type mice but not in AT1a deficient mice. Results suggest Ang II stimulates aldosterone secretion via AT1a and AT1b in the zona glomerulosa and corticosterone secretion via AT1a in the zona fasciculata, and provide first evidence for differential roles of AT1a and AT1b in the adrenals.     

Effects of coenzyme Q on plasma aldosterone concentrations in dogs (author's transl)

The renin-angiotensin system, potassium and adrenocorticotropin (ACTH) are well known as control mechanism for aldosterone secretion. However, the precise mechanism of these factors for aldosterone secretion remain still unclear. Several interesting evidences related to the effects of Coenzyme Q on the secretion and biosynthesis of aldosterone have been demonstrated. Biochemical action of Coenzyme Q is generally accepted as a component of the electron transfer process of respiration in mitochondria. Fabre et al demonstrated that significant reduction of plasma aldosterone concentration in adrenal venous by the Coenzyme Q infusion. Weinstein et al observed that urine sodium excretion decreased after infusion of Coenzyme Q into renal artery. Kumagai et al suggested that Coenzyme Q inhibited the activity of 18-hydroxylase in the adrenal cortex. The present study was designed to evaluate the effects of Coenzyme Q on the secretion of aldosterone. Method: 24 cases of male among el and beagle dogs were subdivided into 4 groups. 1st group were administered intravenous infusion of Coenzyme Q, 2nd group were orally administered Coenzyme Q for 7 weeks, 3rd group were administered simultaneous infusion of Coenzyme Q and angiotensin II and 4th group were administered furosemide orally under the condition of continuous Coenzyme Q administration. Then, plasma concentrations of aldosterone, 11-OHCS and angiotensin I were determined during the time course. Results and Discussions: Plasma aldosterone concentration was significantly increased after intravenous infusion of angiotensin II and decreased 45 minutes after the beginning of infusion. However, the concentration still remained higher than control level. By the simultaneous infusion of Coenzyme Q with angiotensin II, the decreased concentration again increased significantly. It seems that above mentioned results suggest possibility that Coenzyme Q potentiate the action of angiotensin II on aldosterone secretion. By the intravenous infusion of Coenzyme Q, plasma aldosterone concentration increased significantly and concentrations of plasma 11-OHCS and angiotensin I did not affected. This result suggests that Coenzyme Q may stimulate aldosterone secretion from adrenal cortex without increase of ACTH and renin-angiotensin. 4 hours after the oral administration of Coenzyme Q, plasma aldosterone concentration was increased significantly. Na/K in 24 hours' excreta was decreased by Coenzyme Q administration. The decrease of Na/K in excreta may be reflection of the increase of aldosterone secretion. Although, plasma aldosterone concentration increased for the short duration by the Coenzyme Q, it decreased gradually and returned to the control level after 7 days under the condition of continuous oral administration. By the oral administration of furosemide under prolonged Coenzyme Q administration plasma aldosterone concentration increased significantly and remained higher than that of control.     

Novel natriuretic peptide receptor/guanylyl cyclase A-selective agonist inhibits angiotensin II- and forskolin-evoked aldosterone synthesis in a human zona glomerulosa cell line

We report the production of a novel human natriuretic peptide receptor/guanylyl cyclase A (hNPR-A)-selective agonist ANP [G9T, R11S, G16R] (sANP). This agonist has similar affinity to ANP for hNPR-A and 1,000-10,000-fold reduced affinity for the human natriuretic peptide clearance receptor (hNPR-C). sANP was used to directly test the hypothesis that hNPR-A mediates the inhibitory effect of natriuretic peptides on aldosterone generation in a human zona glomerulosa cell line, H295R. Human type A natriuretic peptide and sANP (10(-11) to 10(-6) M) resulted in concentration-dependent increases in cGMP levels and decreases in forskolin (100 nM)- and angiotensin II (5 nM)-induced aldosterone and pregnenolone production. These results revealed an inhibitory effect of both peptides on the agonist-stimulated conversion of cholesterol to pregnenolone (i.e., cytochrome P-450 cholesterol monooxygenase side-chain cleaving enzyme, EC 1.14.15.6). H295R cells also exhibited angiotensin II- and forskolin-evoked conversion of [3H]cortico-sterone to [3H]aldosterone (i.e., cytochrome P-450 steroid 11 beta-monooxygenase/aldosterone synthase, EC 1.14.15.4). Human type A natriuretic peptide and sANP (10(-7) M) inhibited the angiotensin II-stimulated late pathway but did not affect forskolin-facilitated conversion of corticosterone to aldosterone. Our results directly demonstrate inhibitory effects of hNPR-A-mediated signal transduction on cytochrome P-450 cholesterol monooxygenase side-chain cleaving enzyme and steroid 11 beta-monooxygenase/aldosterone synthase complex depending on the steroidogenic agonist used.     

Regulation of interrenal secretion in the axolotl, Ambystoma mexicanum

The regulation of corticosteroid secretion of the adrenal cortex (interrenal tissue) of axolotl (Ambystoma mexicanum) was studied using in vitro preparations of kidney containing interrenal tissue. Normally, 0.3-0.65 ng/5 min corticosterone and 0.15-0.3 ng/5 min aldosterone were released from the tissue. Regulatory peptides were effective in the following range: ACTH = arginine vasotocin > urotensin II > angiotensin II. They stimulate an elevation of corticosterone (plus 0.2-1 ng/5 min) and of aldosterone (plus 0.05-0.15 ng/5 min). The three primary effector systems leading to second messengers, adenylate cyclase (forming cAMP), phospholipase C (forming InsP3 + DAG), and phospholipase A2 (liberating arachidonic acid) are involved in stimulation of biosynthesis. It can be suggested that the second messengers stimulate the biosynthesis at the level of the steps between pregnenolone and corticosterone ('3 beta-hydroxysteroid-dehydrogenase etc.), because the release of corticosterone is more stimulated than aldosterone. This is different than the regulation of anuran interrenal tissue. Ca++ ions are involved in corticosterone secretion. Verapamil inhibits immediately the secretion of corticosteroids and elevation of external Ca++ stimulates the release. It is suggested that Ca++ mediates the secretion process itself. Metamorphosis does not change the response of the interrenal gland compared with the neotenic animal.     

Impact of gender on the renal response to angiotensin II

BACKGROUND: It is clear that women with renal disease progress to end stage at a slower rate than do men. We hypothesized that this protection may result from gender-mediated differences in responses to angiotensin II (Ang II), which has known hemodynamic effects that are thought to promote renal disease progression. We examined sex differences in renin-angiotensin system (RAS) function by measuring renal hemodynamic function and circulating plasma components of the RAS at baseline and in response to graded infusions of Ang II. METHODS: We studied two groups of normal healthy subjects, 24 men and 24 women, mean age 28 +/- 1 years, ingesting a controlled sodium and protein diet. We examined baseline concentrations of angiotensin converting enzyme, plasma renin activity, Ang II, and aldosterone. Inulin and paraaminohippurate clearance techniques were used to estimate effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) at baseline and in response to graded Ang II infusion (0.5, 1.5, and 2.5 ng/kg/min). RESULTS: Mean baseline values for mean arterial pressure and aldosterone were lower in women, whereas values for plasma Ang II, GFR, ERPF, and filtration fraction (FF) did not differ. In response to Ang II, both groups exhibited a similar increase in mean arterial pressure and a decline in ERPF. GFR was maintained during Ang II infusion only in men, resulting in an augmentation of FF. In women, GFR declined in parallel with ERPF, and the FF response was significantly blunted. 17beta-Estradiol plasma concentrations influenced the ERPF response to Ang II infusion, with higher levels predicting a blunting of the decrease. The GFR response was not affected. CONCLUSIONS: The renal microcirculation in sodium-replete women may respond differently to Ang II than that of men, with the female sex predicting a lesser augmentation of FF and possibly a blunted increase in intraglomerular pressure. The mechanism remains obscure, but these contrasting responses may help to explain gender-mediated differences in renal disease progression.     

A delayed suppression of the renin-aldosterone axis following saline infusion in human hypertension

The purpose of this study was to compare the acute suppressibility of the renin-angiotensin-aldosterone (RAA) axis in normotensive (n = 23) and essential hypertensive (n = 62) subjects. Only those hypertensive subjects with normal plasma renin activity (PRA) levels (sodium restricted, upright) were included in the study. Acute suppression of the RAA axis was determined by measuring PRA, plasma angiotensin II (A II), and plasma aldosterone (PA) at frequent intervals during the infusion of isotonic saline (500 ml/hour for 6 hours). Although all parameters fell significantly from control levels by 20-30 minutes in the normotensive subjects, we found that 60% of the hypertensive subjects showed no significant decline in PRA or PA until 120-240 minutes after beginning the infusion. The other hypertensive subjects showed normal RAA suppression. In addition, while there were no significant differences between the three groups in control PRA or PA levels, we found that the PA levels from 30 to 240 minutes during the saline were significantly higher (P less than 0.01) in the hypertensive subjects with delayed suppression. That there were two distinct populations in the hypertensive group was suggested by the bimodality of the frequency response curve, with peaks occurring at 30 and 240 minutes. These studies indicate an abnormality in the acute suppression of the RAA axis in a substantial proportion of subjects with normal renin essential hypertension. Since previous studies in normal subjects have reported that the early phase of response to saline infusion is related to the sodium ion per se and not to intravascular volume expansion, we have come to the conclusion that the present data are consistent with the hypothesis that the delayed suppression hypertensive group has a diminished ability to respond to the sodium ion.     

Effects of ethinylestradiol on the renin-angiotensin-aldosterone-system and on plasma transcortin in women and men

The effects of ethinylestradiol (1 mug/kg body weight daily) on plasma renin substrate concentration, other factors of the renin-aldosterone-system, and on the cortisol-binding capacity of transcortin were determined in 8 young men and 9 young women. The absolute and relative elevation of plasma renin substrate after 5, 14, and 24 days of ethinylestradiol administration was significantly (P less than 0.001) greater in females than males. Control and posttreatment transcortin levels were also higher in women than men, but the percentage increase did not differ between males and females. It is likely that sex differences in the response of plasma renin substrate to the estrogen are due to differences in hepatic synthesis and/or release of renin substrate. In females, plasma renin activity, angiotensin II concentration, and urinary aldosterone excretion rose significantly although less markedly than plasma renin substrate concentration, while in males only the increase in plasma angiotensin II concentration was significant. These results indicate that no safe conclusions on metabolic effects of estrogen treatment in women can be drawn from experiments carried out in male subjects.     

Aldosterone secretion during high sodium cerebrospinal fluid perfusion of the brain ventricles

Conscious sheep with permanent indwelling cannulae in the lateral ventricles and the cisterna magna were Na depleted and then perfused for 9 h with an artificial CSF solution. There were 3 experimental groups: Group I (n=5) received perfusion with aritifical CSF containing NA 170 MEq./1, Group II (n=7) received perfusion with artificial CSF containing Na 145 mEq./1, Group III (n=7) received no perfusion. In Group I the blood aldosterone level fell from 26.4 +/- 7.4 to 8.6 +/- 2.3 ng/100 ml by 9 h after perfusion. There was no significant change in plasma [Na] or [K], blood angiotensin II or plasma renin concentration. Blood cortisol and corticosterone levels rose. There was also a fall in post-perfusion. Group III showed no significant change in blood aldosterone concentration. Multivariate statistical analysis showed that the fall in aldosterone levels during 170 mEq./l Na perfusion could not be accounted for by changes, either alone or together, of ACTH as evidenced by alteration in blood cortisol or corticosterone, or by change of plasma [Na], [K] or renin concentrations. This data supports the hypothesis of an additional factor which may be of CNS origin being involved in the control of aldosterone secretion.     

The effects of age and gender on the pharmacokinetics of irbesartan

AIMS: Single dose pharmacokinetics and safety of irbesartan, an angiotensin II receptor antagonist, were evaluated in healthy young and elderly male and female subjects. METHODS: Irbesartan was administered as two 25 mg capsules after a 10 h fast to 12 young men, 12 young women, 12 elderly men and 12 elderly women. Serial blood and urine sample were collected up to 96 h after the dose. Plasma and urine samples were analysed for irbesartan by h.p.l.c./fluorescence methods. RESULTS: No statistically significant gender effects were observed in peak plasma concentration (Cmax), area under the curve (AUC), and terminal elimination half-life (t1/2) of irbesartan. The geometric mean AUC and Cmax increased by about 43% and 49%, respectively, in the elderly subjects. Also the time to peak was significantly shorter in the elderly subjects compared with that observed in the young subjects. Renal clearance ofirbesartan was significantly reduced in the elderly females but this reduction is not likely to be of any clinical relevance since less than 3% of the administered dose of irbesartan is excreted unchanged in the urine. CONCLUSIONS: Although there was an effect of age on the pharmacokinetics of irbesartan, based on the safety and efficacy profile, no adjustment in irbesartan dosage is necessary with respect to age or gender.     

Circulating plasma prekallikrein and tissue kallikrein in normotensive and hypertensive humans: effects of angiotensin II infusion

Kinins lower blood pressure but the stimuli leading to kinin generation and their origin are less well known. We administered angiotensin II in graded infusion doses to patients with primary hypertension and normotensive controls to study the effects of on circulating kallikreins. Angiotensin II infusion did not significantly alter plasma prekallikrein or tissue kallikrein levels and the plasma levels and their changes did not correlate with blood pressure levels or changes. In the normotensive group prekallikrein levels and renin activity correlated negatively with urinary sodium and chloride excretion during basal conditions and partially during the infusion. U-tissue kallikrein concentration increased in the normotensive group. Thus, acute elevation of blood pressure induced by angiotensin II does not activate the circulating kallikrein-kinin systems. Data rather indicate that the circulating kallikrein-kinin systems may be related to alterations in volume and sodium balance and that these mechanisms may be altered in primary hypertension.     

Pregnenolone-binding proteins in the rat adrenal cortex

Rat adrenal cortex contains a protein(s) that binds pregnenolone with high affinity. This binding, demonstrated by gel filtration and by a dextran-coated charcoal method, was associated with the cytosol and with fractions solubilized by sonication from the mitochondria and microsomes. The binding of pregnenolone was saturable and was inhibited by mercurials and proteolytic enzymes. Pregnenolone-binding was not influenced by the presence of progesterone, deoxycorticosterone, corticosterone or aldosterone, but was inhibited by steroids with a 3beta-hydroxy-5-ene structure similar to pregnenolone, and by hydroxymethylene steroid and cyanoketone. We suggest that this protein is involved in the intracellular transport and retention of pregnenolone within adrenal cortical cells.     

ACE (I/D) genotype as a predictor of the magnitude and duration of the response to an ACE inhibitor drug (enalaprilat) in humans

BACKGROUND: We have investigated the possible effects of contrasting ACE (I/D) genotypes on the responses to the ACE inhibitor enalaprilat in normotensive men. METHODS AND RESULTS: Subjects with DD (n=12) and II (n=11) ACE genotypes received an intravenous infusion of enalaprilat or placebo. Pressor responses to stepwise, incremental doses of angiotensin I were measured at 1 and 10 hours after dosing. The dose required to raise mean blood pressure by 20 mm Hg (PD20) was calculated individually, and the ratio of PD20 during enalaprilat to that during placebo (dose ratio, DR) was used for assessment of the extent of ACE inhibition. The pressor response was significantly attenuated at 1 hour after enalaprilat in both groups, but significant attenuation was evident at 10 hours after dose only in the II subjects. The DRs at both 1 hour (median, 5.43 versus 2.82, P=0.0035) and 10 hours (2.06 versus 0.84, P=0.0008) after enalaprilat were significantly higher in II subjects than in DD subjects. CONCLUSIONS: The effect of enalaprilat was significantly greater and lasted longer in normotensive men homozygous for the II ACE genotype. By multivariate analysis, ACE (I/D) genotype and plasma angiotensin II levels were predictive of >50% of the variation in response to ACE inhibition.     

Inhibition of the reoxidation of the secondary electron acceptor of photosystem II by bicarbonate depletion

Intravenous infusion of 600 ng/kg/min of 1-sarcosine, 8-isoleucine-angiotensin II, an angiotensin II antagonist, caused a marked blood pressure fall and a decrease in plasma aldosterone in 3 patients with Bartter's syndrome. These results indicate that proximal cause of Bartter's syndrome is an arteriolar hyporesponsiveness to angiotensin II and that this angiotensin II analogue has an antagonist activity on peripheral arterioles as well as adrenal cortex.     

An academic paradox: high school students'' perceptions of their class standing and self-reported risk-taking

OBJECTIVE: To determine whether the effects of angiotensin I (AngI) in humans can be explained entirely by its plasmatic conversion to angiotensin II (AngII). METHODS: Ten healthy male volunteers on a sodium-restricted diet were studied on two separate occasions. during which, in random order, AngI or AngII was infused in increasing doses of 0.3, 1 and 3 pmol x kg-1 x min-1. Mean arterial pressure (MAP), effective renal plasma flow (ERPF), glomerular filtration rate (GER), active plasma renin concentration (APRC), AngII, aldosterone (Aldo) and catecholamines were assessed at baseline, after each dose of AngI or AngII and 30 and 60 min after discontinuation of the AngI/AngII infusion. RESULTS: The rise in plasma AngII was significantly less during AngI infusion as compared to AngII infusion (P < 0.05). Changes in MAP, Aldo and GFR, however, were compatible during both infusions. In the kidney, on the other hand, the decrements in APRC and ERPF during AngII infusion exceeded those during AngI (P < 0.05). After cessation of either infusion. AngII concentrations, MAP, ERPF and Aldo returned to baseline levels within 1 h. Renin, however, was still significantly inhibited at that time (P < 0.05). Catecholamines remained virtually unchanged during all experiments. CONCLUSIONS: Our data show that AngI and AngII have similar effects on blood pressure and Aldo, but they differ in their renal effects. The latter may be due to a low renal capacity to convert AngI. The prolonged inhibition of renin release after cessation of the infusions may be caused by reduced renin mRNA expression or by accumulation of AngII in the kidney.     

Effects of angiotensin II and its blockers Sar1-Ile8-angiotensin II and DuP 753 on drinking in ducks in relation to properties of subfornical organ neurons

Properties of systemically applied angiotensin II in stimulating water intake of normally hydrated ducks were studied and the results compared with properties of angiotensin II-responsive neurons of the subfornical organ which are considered as targets for circulating angiotensin II acting as a dipsogen. Following intravenous infusion of hypertonic saline (2000 mosmol.kg-1 at 0.3 ml.min-1 for 1 h), intravenous infusion of 0.3 ml.min-1 isotonic saline with angiotensin II (200 ng.min-1), starting 1 h later, stimulated drinking in each case at an angiotensin II plasma level of about 1400 pg.ml-1. Without hypertonic priming, the same angiotensin II infusion did not stimulate drinking in each experiment; however, if effective, repeated infusions of ANGII induced stable dipsogenic responses. Angiotensin II infusions did not alter plasma levels of antidiuretic hormone. Sar1-Ile8-angiotensin II, a non-selective angiotensin II antagonist, acted weakly as a partial agonist when infused at a dose 200-fold higher than angiotensin II and effectively blocked the dipsogenic action of angiotensin II; this corresponds to the inhibition of angiotensin II-induced excitation by Sar1-Ile8-angiotensin II observed in duck subfornical organ neurons. DuP 753 (losartan), an angiotensin II antagonist specifically blocking AT1 receptors in mammals, had equivocal effects on angiotensin II-induced drinking in ducks at rates 50- and 200-fold higher than angiotensin II, which corresponds to the weak inhibitory action of this compound on angiotensin II-induced neuronal excitation in the duck SFO. Blood pressure was only marginally elevated by the applied angiotensin II dose and Sar1-Ile8-angiotensin II had no effect.     

Dependence of adrenalectomy-induced sodium appetite on the action of angiotensin II in the brain of the rat.

Adrenalectomized rats express a robust sodium appetite that is accompanied by high levels of blood-borne angiotensin II and is caused by angiotensin II of cerebral origin. Blood-borne angiotensin II is elevated in rats consuming NaCl after adrenalectomy, and plasma angiotensin II concentrations are increased further when the animals cannot drink a NaCl solution. These phenomena are the result of the pathological removal of aldosterone, because replacement therapy returned both sodium intake and plasma angiotensin II concentrations to preadrenalectomy levels. The adrenalectomized rat's appetite for sodium is completely suppressed by interference with the central, but not the peripheral, action of angiotensin II. These data demonstrate that the mechanism of the sodium appetite of the adrenalectomized rat is a pathological instance of the angiotensin/aldosterone synergy that governs the sodium appetite of the adrenal-intact, sodium-depleted rat. Because aldosterone has been removed, angiotensin acts alone to produce the appetite. Furthermore, the data show that it is angiotensin II of central origin that is important for sodium appetite expression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nocturnal polyuria and natriuresis in male patients with nocturia and lower urinary tract symptoms

PURPOSE: We investigated the circadian variation in urine output, plasma angiotensin II, aldosterone, atrial natriuretic peptide, arginine vasopressin and blood pressure. MATERIALS AND METHODS: We studied 17 elderly men with nocturia and lower urinary tract symptoms, and 10 age matched controls without nocturia. RESULTS: Of the 17 patients studied 11 had a lack of diurnal variation in urine output and increased nocturnal urine production associated with increased nocturnal sodium excretion, and 6 had a diurnal variation in urine output comparable to controls. CONCLUSIONS: Nocturia in a large proportion of elderly men with lower urinary tract symptoms is caused by nocturnal polyuria and natriuresis.     

The renin-angiotensin-aldosterone system in mother and fetus at term

Plasma renin activity, renin substrate, angiotensin II, aldosterone and cortisol were measured concurrently and renin concentration calculated in plasma from mothers during labor and delivery, from cord and from newborn infants. The renin-angiotensin-aldosterone system was found strongly stimulated in both mother and fetus. The high values of plasma renin activity in fetus were due exclusively to the high renin concentrations the substrate concentration being normal. In the mother, however, the markedly elevated renin substrate resulted in a doubling of relative values of renin activity compared to renin concentration. Therefore gradients of renin and renin substrate across the placenta are established, but the resulting renin activity is similar on both sides and the levels of generated angiotensin II are also nearly indentical with a good correlation between these last parameters. Aldosterone is as elevated in mother as in fetus whereas cortisol, due to its binding to transcortin, is twice as high in mother as in fetus. No correlation was found between renin activity or concentration of angiotensin II and aldosterone or cortisol indicating that other factors controlling aldosterone are involved.