Urinary excretion of aldosterone metabolite Kelly-M1 in patients with adrenal dysfunction

Using tetrahydroaldosterone antibody a radioimmunoassay was developed to measure substance Kelly-M1 (K-M1) in human urine. The normal values were lower than observed by Kelly et al. who discovered the catabolite after giving large doses of exogenous aldosterone. While in essential hypertension the excretion of K-M1 was predominantly within the normal range, elevated values were found in most cases of 21-hydroxylase deficiency, both the simple virilizing and salt losing form, primary aldosteronism, renal hypertension and cystinosis. Our findings suggest that K-M1 may be formed from 21-deoxyaldosterone and/or by microbial intervention from aldosterone or its metabolites.     

Role of intestinal bacteria in the metabolism of aldosterone in man

Urinary aldosterone metabolites were measured before and after the administration of 1 g/day of kanamycin, a nonabsorbable antibiotic, for 7 days, in 6 normal volunteers and in 11 patients with liver cirrhosis. Urinary excretion of 21-deoxytetrahydroaldosterone (21-deoxy-THAldo) decreased by 40 and 86% from the control values in normal volunteers and in patients, respectively (p less than 0.05), after kanamycin administration. Urinary excretion of 21-deoxyaldosterone (21-deoxy-Aldo) also fell by 48 and 89% in normal subjects and in patients, respectively, but the decrease was significant only in the normal subjects (p less than 0.05). In normal volunteers, urinary free aldosterone and THAldo remained constant, whereas the ratio of 21-deoxy-Aldo to aldosterone and 21-deoxy-THAldo to THAldo decreased from 10.2 to 3.7 and 2.1 to 0.3, respectively (p less than 0.01). These results indicate that intestinal bacteria participate in the metabolism of aldosterone during enterohepatic circulation in man.     

A paradox: elevated 21-hydroxypregnenolone production in newborns with 21-hydroxylase deficiency

21-Hydroxypregnenolone and its metabolite 5-pregnene-3 beta, 20 alpha 21-triol have been measured in the sulfate fraction of neonatal urine. These two steroids are the major two 21-hydroxylated 5-pregnenes produced by neonates and are almost exclusively excreted as disulfates. The excretions of these steroids by normal infants and infants with 21-hydroxylase deficiency were compared. In addition to measurement of the absolute excretion, the excretion relative to the total 3 beta-hydroxy-5-ene output was also determined. The results show that 21-hydroxypregnenolone excretion is highly elevated in 21-hydroxylase deficiency (affected, mean 887 micrograms/24 h, range 453-1431 micrograms/24 h; normal, mean 117 micrograms/24 h, range 17-263 micrograms/24 h), but when compared to excretion of other delta 5 steroids the excretion is slightly low [(21-hydroxypregnenolone + 5-pregnene-3 beta, 20 alpha, 21-triol)/total 3-beta-hydroxy-5-ene steroids, 2.9% affected; 3.6% normal]. This difference was not statistically significant. There is thus no evidence that the 21-hydroxylase acting on pregnenolone is deficient in congenital adrenal hyperplasia. The explanation of the normal activity of "pregnenolone 21-hydroxylase," although not clearly defined, is probably associated with two recent findings by other workers: (a) that the human fetus has an active 21-hydroxylase distinct from the adrenal enzyme and (b) that a 21-hydroxylase structurally very different from the adrenal enzyme, with high activity towards pregnenolone (but no activity towards 17-hydroxyprogesterone), has been isolated from rabbit hepatic microsomes.     

Radioimmunoassay of tetrahydroaldosterone in urine]

A radioimmunoassay for urinary tetrahydroaldosterone is described. An antiserum, elicited by a 3-carboxy-methyloxime 18-21 aldosterone diacetate conjugated to bovine serumalbumine, with which tetrahydroaldosterone cross reacts, is used. The method is specific, sensitive (10 pg/tube), accurate, reproducible (7%), thus allowing sufficient reliability for clinical applications. In 19 normal adults subjects under unrestricted sodium intake, the urinary tetrahydroaldosterone averaged 59,8+/-29,4 mug/24 h.     

18-oxocortisol: effect of dexamethasone, ACTH and sodium restriction

The urinary excretion of 18-oxocortisol in 37 normal subjects consuming a normal sodium diet was 1.2 +/- 0.9(SD) microgram/24 h. Dexamethasone administration to 5 normal individuals suppressed the excretion of 18-oxocortisol from 1.16 +/- 0.5 micrograms/24 h to 0.6 +/- 0.2 micrograms/24 h. While they still received dexamethasone, ACTH administration raised the 18-oxo-cortisol excretion to 3.82 +/- 1.2 micrograms/24 h. Seven normal subjects were placed on a sodium restricted diet, and the urinary excretion of 18-oxocortisol rose from 1.5 +/- 1.21 micrograms/24 h to 8.54 +/- 5.08 micrograms/24 h and aldosterone from 6.6 +/- 2.0 micrograms/24 h to 39.7 +/- 14.6 micrograms/24 h. Two of the seven individuals showed minimal increases in the excretion of 18-oxocortisol, but in all cases aldosterone increased with sodium restriction. The urinary excretion of 18-oxocortisol correlated significantly with the excretion of aldosterone, 18-hydroxycortisol, cortisol, and 19-nordeoxycorticosterone. These studies indicate that 18-oxocortisol secretion is under ACTH regulation, but since sodium restriction also increases the excretion of 18-oxocortisol, the renin-angiotensin system must also participate in its regulation. However, some individuals do not increase their excretion of 18-oxocortisol with sodium restriction, although aldosterone excretion increases as expected, suggesting that additional factors participate in the regulation of 18-oxocortisol production.     

Urinary N tau-methylimidazole acetic acid excretion in respiratory disease

N tau-methylimidazole acetic acid (N tau-MIAA) is the principal urinary metabolite of histamine. The basal urinary excretion rate of N tau-MIAA was determined as 0.117 +/- 0.008 (SE) mg/h, with a renal clearance for N tau-MIAA of 273 +/- 27 ml/min implying active secretion. After subpharmacological infusion of histamine (50 ng.kg-1.min-1 over 2 h) in five volunteers that increased plasma histamine from 0.28 +/- 0.04 to 0.71 +/- 0.15 ng/ml, urinary excretion of N tau-MIAA over 8 h was increased by less than 17% compared with a control saline infusion. Urinary N tau-MIAA excretion in normal controls (273 +/- 14 micrograms/mmol creatinine) was similar to that observed in patients with severe acute asthma (253 +/- 22 micrograms/mmol), antigen-induced bronchoconstriction (269 +/- 21 micrograms/mmol), seasonal allergic rhinitis (304 +/- 31 micrograms/mmol), and clinically stable bronchiectasis (270 +/- 22 micrograms/mmol). In contrast, large increases in metabolite excretion (greater than 7,000 micrograms/mmol creatinine) were observed in a patient with systemic mastocytosis where very high plasma histamine levels were recorded (greater than 500 ng/ml) and marked systemic hemodynamic effects occurred. We conclude that urinary N tau-MIAA will only be increased in pathologies where sustained hyperhistaminemia occurs and that increased local histamine production in the lung or the upper airway does not cause a measurable change in the basal urinary excretion of this metabolite.     

A new approach to the difficult assessment of aldosterone secretion in anephric patients.

A new method for the assessment of endogenous formation of aldosterone in anephric patients is described. (1, 2-3H) aldosterone was administered i.v. to patients 1-2 days before hemodialysis, and then the specific activity (SA) of tetrahydroaldosterone glucosiduronate, the major aldosterone metabolite, was measured in the dialysate using a specific radioimmunoassay. The aldosterone secretion rate was determined from the extent of isotope dilution by endogenous metabolite. Aldosterone secretion rates measured in 10 patients were for the most part low. The secretion rate determined in blood from the aldosterone metabolic clearance rate and plasma aldosterone concentration closely approximate secretion rate values obtained by the isotope dilution method in 3 of 4 patients. In 2 patients in whom ACTH was administered chronically, radio-labeled aldosterone was administered at the start of the study and then the day to day aldosterone secretory response to ACTH was determined from the SA of tetrahydroaldosterone in blood. Aldosterone secretion continuously increased for as long as ACTH was administered.     

Role of 21-deoxyaldosterone in human hypertension

21-Deoxyaldosterone has been postulated to be a precursor of aldosterone in an altenative biosynthesis pathway and Kelly's-M1 is considered to be its metabolite. In healthy volunteers, the excretion rate of 21-deoxyaldosterone and of Kelly's-M1 are significantly lower than the aldosterone metabolites, aldosterone-18-glucuronide and tetrahydro-aldosterone and than the aldosterone precursor 18-OH-corticosterone. Essential hypertension patients (with low and normal renin) excrete comparable values of 21-deoxyaldosterone and Kelly's-M1 as normotensives. In 66% of aldosterone-producing adenoma cases (APA) and in 60% of idiopathic hyperaldosteronism (IHA) patients, significantly raised values of 21-deoxyaldosterone and Kelly's-M1 were found. The patients with the high excretion rates of both steroids showed only moderately increased values of the aldosterone metabolites, aldosterone-18-glucuronide and tetrahydro-aldosterone, as well as of the aldosterone precursor 18-OH-corticosterone. In contrast, the latter mentioned steroids were excreted in higher amounts in those patients with normal excretion of 21-deoxyaldosterone and Kelly's-M1. Hence, it is suggested that aldosterone is produced alternatively either via 18-OH-corticosterone alone or additionally via 21-deoxyaldosterone. Furthermore, in three cases of “incidentally” discovered adrenal adenomas, 21-deoxyaldosterone and Kelly's-M1 were the only elevated steroids. After adrenalectomy, excretion of 21-deoxyaldosterone and of Kelly's-M1 and blood pressure returned to normal, which proves that these steroids play a role in blood pressure regulation. In essential hypertension, ACTH infusion induced a significant increase of 21-deoxyaldosterone and Kelly's-M1. However, the increase after angiotensin II was 3- to 6-fold higher than after ACTH. IHA patients proved to be more responsive to angiotensin II; and, in contrast, APA cases proved to be more sensitive to ACTH. The data suggest that beside the main route of aldosterone biosynthesis via 11-deoxycorticosterone, corticosterone and 18-OH-corticosterone an alternative pathway exits via 21-deoxyaldosterone in healthy and in hypertensive patients. There are similarities between the regulation of 21-deoxyaldosterone and the regulation of aldosteorne. The determination of 21-deoxyaldosterone and its possible metabolite Kelly's-M1 might be appropriate in the diagnosis of mineralocorticoid-induced forms of hypertension, especially when an adrenal adenoma is discovered.     

19-Noraldosterone in pregnancy-induced hypertension

Pregnancy-induced hypertension (PIH) is a frequent cause of maternal and neonatal morbidity and mortality. 19-Noraldosterone, which was shown to be synthesized in the human adrenal gland, exhibits potent mineralocorticoid and hypertensive activity. To examine the role of mineralocorticoids in the pathophysiology of PIH, we studied urinary 19-noraldosterone, tetrahydroaldosterone, free cortisol, and cortisone concentrations and mineralocorticoid receptor levels in peripheral blood mononuclear leukocytes, from 17 women with PIH and 16 normal pregnant women as controls. Sequence analysis of the mineralocorticoid receptor gene in PIH patients was also done. The 24-h urinary excretion of 19-noraldosterone was significantly lower in PIH (120 +/- 38 pmol/day) than in controls (358 +/- 55 pmol/day) (P < 0.05). Urinary tetrahydroaldosterone was also decreased in PIH compared with controls. Ratios of urinary free cortisol to cortisone (a measure of 11beta-hydroxysteroid dehydrogenase 2 activity) did not differ significantly between groups. Mineralocorticoid receptor density was significantly (P < 0.05) decreased in the PIH group (133 +/- 15 binding sites/cell) compared with controls (255 +/- 21 binding sites/cell). No mutations were found in the coding region of the mineralocorticoid receptor gene in PIH. These results suggest that circulating aldosterone, 19-noraldosterone, and renal 11beta-hydroxysteroid dehydrogenase2 do not contribute to the pathogenesis of PIH. Regulatory factors that cause the down-regulation of the mineralocorticoid receptor in PIH should be clarified.     

Urinary 18,19-dihydroxycorticosterone and 18-hydroxy-19-norcorticosterone excretion in patients with primary and secondary aldosteronism.

18,19-Dihydroxycorticosterone (18,19(OH)2-B) and 18-hydroxy-19-norcorticosterone (18-OH-19-nor-B) measurements were carried out on the urine of patients with primary aldosteronism (PA), essential hypertension (EHT), and liver cirrhosis with (LC, SA (+)) and without (LC, SA (-)) aldosteronism. The separation of these steroids was performed by extraction and high-performance liquid chromatography followed by radioimmunoassay (RIA) with specific antibodies prepared in our laboratory. 18,19(OH)2-B excretion was elevated in patients with PA (24 +/- 5.9 [+/- SE] micrograms/24 hr; n = 15) and LC, SA (+) (83 +/- 9.4 micrograms/24 hr; n = 8). Values in LC, SA (-) (3.1 +/- 1.2 micrograms/24 hr; n = 8) and in EHT (3.7 +/- 0.4 micrograms/24 hr; n = 42) were found to be similar to those in normal subjects (5.5 +/- 0.9 micrograms/24 hr; n = 30). The values of urinary 18-OH-19-nor-B in PA and LC, SA (+) were higher than in LC, SA (-) EHT and normal subjects (P less than 0.05). Values in the latter three groups, as compared with each other, did not show significant alterations. Nothing is known about the biologic relevance of 18,19(OH)2-B and very little about that of 18-OH-19-nor-B, but the latter steroid seems to potentiate experimental renal hypertension. One can speculate about possible roles of both steroids as precursors of other steroids, e.g., the biologically potent mineralocorticoid 19-noraldosterone. The data obtained suggest that it is not relevant to measure the urinary levels of either steroid in these clinical syndromes.     

Effects of corticotropin-releasing factor (CRF) on aldosterone and 18-hydroxycorticosterone in essential hypertension and primary aldosteronism

The effects of ovine corticotropin releasing factor (o-CRF) on plasma aldosterone, 18-OH-corticosterone (18-OHB), plasma adrenocorticotropin (ACTH) and cortisol were determined in eight patients with primary aldosteronism, six with aldosterone-producing adenoma (APA) and two with idiopathic hyperaldosteronism (IHA). The results were compared with those in six normal subjects and eleven patients with essential hypertension (EHT, 5 with low renin and 6 with normal renin). In patients with APA, the peak plasma aldosterone and 18-OHB responses to 100 micrograms iv of o-CRF (226% and 113% increase from baseline, respectively) were greater than those in EHT and normal subjects. The net integrated aldosterone and 18-OHB responses (840 +/- 156, and 419 +/- 121 ng/dl.hr, respectively) were also significantly greater (p less than 0.01) in APA than those in normals and EHT. In two patients with IHA, both the peak and net integrated aldosterone response were smaller than those in APA, in spite of nearly identical plasma ACTH and cortisol responses. These results suggest that augmented responses of mineralocorticoids to o-CRF may be characteristic of aldosteronism due to APA, mediated by CRF-induced ACTH, and possibly other proopiomelanocortin (POMC)-derived peptides.     

Urinary dopamine, noradrenaline and adrenaline in type 2 diabetic patients with and without nephropathy

We measured the urinary excretions of dopamine, noradrenaline and adrenaline, their conjugated metabolites, urinary excretion of sodium and creatinine clearance simultaneously in 21 patients with Type 2 (non-insulin-dependent) diabetes and 6 normal subjects. The mean (+/- SEM) value for urinary excretion of dopamine (52.4 +/- 8.8 micrograms/day) in diabetic patients with nephropathy (Group C, n = 12) was significantly lower (P less than 0.01) than in the normal subjects (Group A, 179.7 +/- 15.5 micrograms/day) and in diabetic patients without nephropathy (Group B, n = 9, 131.5 +/- 16.5 micrograms/day). The mean values for the urinary excretions of noradrenaline and adrenaline were also significantly lower (P less than 0.01) in Group C than in Groups A and B. In addition, the mean urinary excretion of conjugated metabolite of dopamine in Group C was significantly lower (P less than 0.05) than in Group A. There was a trend toward the observation that the mean 24-h urinary excretion of sodium in Group C (121.6 less than 12.9 mEq) was lower as compared with that in Group A (140.8 +/- 8.9 mEq) or B (150.7 +/- 17.9 mEq). A multiple regression analysis revealed that the 24-h urinary excretion of dopamine correlated significantly with creatinine clearance, systolic (P less than 0.01) and diastolic (P less than 0.05) blood pressures. The results indicate that synthesis or secretion of renal dopamine might decrease with a progression of diabetic nephropathy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of aldosterone by sephadex LH-20 chromatography and radioimmunoassay

A method for the determination of urinary aldosterone has been developed which appears to be applicable for the clinical laboratory. Ten ml of urine were used for analysis. The purification of aldosterone consisted of hydrolysis at pH 1.0; CH₂Cl₂ extraction and column chromatography on Sephadex LH-20. Recovery of added 4-¹⁴C-D-aldosterone was 44.7 + 7.1 (2 SD) % for 60 experiments. The extraction was followed by a rapid radioimmunoassay analysis of aldosterone. The sensitivity of the overall assay was 1.6 μg aldosterone, the accuracy 92.0 ±3.4 %. The coefficient of variation was within one assay 14 % for a given sample (n = 19) and 20 % for multiple assays. Excretion of aldosterone as determined in 17 healthy individuals on an uncontrolled diet was 9.5 ± 3.6 (SD) μg per 24 hours. Patients suffering from renal arterial stenosis or from essential hypertension presented an increase of aldosterone excretion upon sodium restriction. An increased excretion of aldosterone without any response to reduced sodium uptake was found in patients with primary aldosteronism.     

Serum aldosterone and protein-binding variables in Yanomama Indians: a no-salt culture as compared to partially acculturated Guaymi Indians

Yanomama Indians from the jungles of southern Venezuela and northern Brazil excreted 1 +/- 1.5 mEq of Na and 203 +/- 109 mEq of K and had low blood pressure (BP), 102/62 mm Hg). In comparison, Guaymi Indians of Panama excreted 103 +/- 50 mEq of Na and 118 +/- 52 mEq of K and had significantly higher BP (114/75 mm Hg, p less than 0.001). Elucidating the renin-aldosterone axis, total upright serum aldosterone in 34 Yanomama was high (85.6 +/- 78 ng/100 ml). The binding capacities of thermolabile (ABG) and thermostable (ABG-Ts) serum globulins for aldosterone were elevated at 23.8 +/- 6 and 14.9 +/- 2.6%, respectively; consequently, total ABG- plus ABG-Ts- bound aldosterone was as high as 38.6 +/- 6.3%. Plasma renin activity (PRA 10.3 +/- 2.4 ng/ml/h) and urinary aldosterone 18-glucuronide (70.3 +/- 30 micrograms/24 h) in 17 Yanomama were also very high. In contrast, total serum corticosteroids and corticosteroid-binding globulin (CBG) binding capacity were normal, suggesting normal ACTH activity. PRA correlated positively with total (r = 0.47, p less than 0.05) and free (r = 0.47, p less than 0.05) serum aldosterone, which in turn showed a negative trend with Na (r = 0.33, NS) excretion. The effect of high dietary K appeared less important to aldosterone stimulation and PRA suppression. ABG-bound aldosterone (r = 0.43, p less than 0.01) as well as ABG-Ts (r = 0.56, p less than 0.05) were negatively correlated with diastolic but not systolic BP. The total ABG- and ABG-Ts-bound fraction correlated with diastolic BP (r = 0.43, p less than 0.05) in contrast to the free fraction (r = 0.08, NS) or total aldosterone (r = -0.09). Apparently, only bound serum aldosterone is important for the maintenance of diastolic BP. High serum aldosterone, with elevated excretion, indicates an increased secretion rate; increased serum protein binding suggests an increased tissular activity and alterations in aldosterone metabolism. In Guaymi Indians both total plasma aldosterone (14.5 +/- 65 ng/100 ml) and urinary aldosterone (8.1 +/- 4.8 micrograms/creatinine excretion) were normal. ABG-binding capacity for aldosterone was moderately elevated (17.8 +/- 4.8) and of ABG-Ts normal (10.2 +/- 1.2) suggesting a nearly normal aldosterone metabolism and regulation. The BP of Guaymi was significantly higher than that of the Yanomama.     

The Influence of a Heparin-Like Compound on Hypertension,Electrolytes and Aldosterone in Man

The mechanisms of the aldosterone-inhibiting and antihypertensive actions of heparin and certain other sulfated mucopolysaccharides were investigated in 13 hypertensive patients. N-formyl chitosan polysulfuric acid (RO 1-8307) was used rather than heparin because of its low anticoagulant activity. RO 1-8307 lowered aldosterone secretion in one patient with proved and one with probable primary aldosteronism; this indicates that the mucopolysaccharide does not inhibit aldosterone secretion via the renin-angiotensin mechanism. In six hypertensive patients RO 1-8307 caused a fall in the secretion of aldosterone and its probable immediate precursor, 18-hydroxycorticosterone; therefore it does not act at the last step in the synthesis of aldosterone. RO 1-8307 produced a prolonged clinical and biochemical remission in the two patients considered to have primary aldosteronism but did not influence blood pressure in five of seven patients in whom excessive aldosterone was probably not a major factor in the hypertension. It is concluded that the antihypertensive action of RO 1-8307, and perhaps of heparin as well, is largely due to suppression of aldosterone secretion.     

Serum zinc and angiotensin-converting enzyme levels in patients with lung cancer

Forty-two patients with lung cancer and 72 healthy subjects were studied in order to determine a possible relationship between serum zinc and angiotensin-converting enzyme (ACE), a peptidyl dipeptide hydrolase. Serum zinc levels were 105 +/- 21 micrograms/dl in control subjects and 50 +/- 19 micrograms/dl in patients, and angiotensin-converting enzyme activity was 296 +/- 28 U/l in the former and 240 +/- 55 U/l in the latter using hippurylglycylglycine as a substrate. The findings obtained show that the decreased levels of angiotensin-converting enzyme may be related to decreased serum zinc levels and that the primary defect may be the zinc deficiency in these patients.     

Role of atrial natriuretic peptide in mineralocorticoid escape phenomenon in patients with primary aldosteronism

The withdrawal effect of spironolactone treatment on natriuresis was studied in relation to atrial natriuretic peptide (ANP) in five patients with primary aldosteronism due to adenoma. The patients had been treated with spironolactone for 2-3 months before they were admitted. After admission, blood pressure, body weight, and urinary excretion of sodium were measured daily. Venous samples were obtained twice a week for measurements of plasma levels of ANP, plasma renin activity (PRA), and plasma concentrations of aldosterone (PAC), cortisol, and deoxycorticosterone. The study was performed for 7 days during the treatment with spironolactone and for 18 days after stopping the administration. Plasma volume was determined two times, during the control period and on the 13th day after stopping spironolactone. Urinary sodium excretion decreased initially and returned to the control levels successively. Body weight and plasma volume increased, and blood pressure rose steadily. PRA and the plasma concentrations of cortisol and deoxycorticosterone decreased significantly (P less than 0.05); however, high levels of PAC did not alter significantly. Plasma ANP levels increased significantly (P less than 0.05) from 26 +/- 4 pg/ml during the control period to 195 +/- 47 pg/ml on the 13th day after stopping spironolactone. The data of the urinary sodium excretion showed the escape from sodium-retaining effect of aldosterone, and this escape could be explained by the increase in plasma ANP. Furthermore, ANP might contribute to the decrease in cortisol and deoxycorticosterone in plasma because of the direct inhibitory action of ANP on steroidogenesis.     

Influence of glucocorticoid on the metabolism of aldosterone in the isolated perfused rat liver and kidney.

The effect of glucocorticoid deficiency and excess on the extraadrenal metabolism of D-[4-14C]aldosterone (at 4 nM) was studied by radioimmunoassay and by high-performance liquid chromatography in the isolated perfused liver and kidney of adult Wistar rats. Bilateral adrenalectomy was performed 3 weeks before experiments. In nonadrenalectomized rats, 0.3 mg/kg/day dexamethasone was continuously infused subcutaneously for 1 week before experiments. Adrenalectomy did not affect hepatic or renal metabolism of aldosterone. Dexamethasone treatment did not change the renal handling of aldosterone. However, the hepatic clearance of aldosterone was 19% lower (P less than 0.05) in livers of dexamethasone treated rats than in livers of normal rats. After 5 minutes, perfusate [4-14C]aldosterone metabolites were lower in livers of dexamethasone-treated than in livers of normal rats (P less than 0.05). Similar perfusate levels were then obtained. Radiometabolite peaks with similar relative retention times were found in the hepatic perfusate of all groups. However, the ratio between circulating polar metabolites of aldosterone and the metabolites less polar than tetrahydroaldosterone, after 5 and 15 minutes, was highest in livers of dexamethasone-treated rats. Biliary elimination of 14C was similar in all groups. Significant amounts of conjugated tetrahydroaldosterone were only excreted in the bile of dexamethasone-treated rats. In conclusion, glucocorticoid excess reduced the hepatic clearance of aldosterone and changed the pattern of the hepatic metabolites of aldosterone both in circulation and in bile.     

Reduced urinary aldosterone excretion rates with normal plasma concentrations of aldosterone in the very elderly

Although aldosterone production declines with age, so does the aldosterone metabolic clearance rate (MCR), and the net effect of age on the circulating level of aldosterone may be less than can be predicted from production rates alone. The effect of age on aldosterone production and plasma levels was studied in a group of elderly individuals at a very advanced age when susceptibility to the impacts of age might be particularly pronounced. Seventeen nursing home patients, ages 75-99 (mean age 86 years), had aldosterone production assessed from the urinary excretion rate of the acid hydrolyzable 18-glucuronide conjugate of aldosterone. Aldosterone excretion was low in the elderly when compared to a group of healthy, young to middle-aged subjects: 123 +/- 19 (SEM) vs. 234 +/- 18 ng/h (P less than 0.001). However, plasma aldosterone concentrations in the elderly were well within a range observed in much younger and fully ambulatory subjects: 14.1 +/- 1.3 in the elderly vs. 15.9 +/- 1.8 ng/dL in the young. The plasma aldosterone concentration was apparently maintained at a normal level by a coincident decrease in both the metabolic clearance rate and the aldosterone production rate. In conclusion, an aldosterone deficiency state resulting from an age-correlated reduction in aldosterone production is probably uncommon in the elderly.     

Determination of functional effects of mutations in the steroid 21-hydroxylase gene (CYP21) using recombinant vaccinia virus

Steroid 21-hydroxylase (P450c21) is absent or defective in more than 90% of patients with congenital adrenal hyperplasia. This disorder of cortisol biosynthesis occurs in a wide spectrum of clinical severity; specific mutations in the 21-hydroxylase gene (CYP21) have been found in association with particular clinical phenotypes. To determine the functional effects of mutations causing amino acid substitutions, normal P450c21 and three mutagenized P450c21 enzymes were expressed at high levels in cultured COS-1 cells using recombinant vaccinia virus. A single amino acid substitution (Val281----Leu) present in patients with mild "nonclassical" 21-hydroxylase deficiency resulted in an enzyme with 20-50% of normal activity. A mutation (Ile172----Asn) identified in patients with the "simple virilizing" form (poor cortisol synthesis but adequate aldosterone synthesis) resulted in an enzyme with less than 2% of normal activity. Finally, a cluster mutation (Ile-Val-Glu-Met234-238----Asn-Glu-Glu-Lys) found in a patient with severe "salt wasting" 21-hydroxylase deficiency (inadequate aldosterone synthesis) results in an enzyme with no detectable activity. These data indicate that the severity of 21-hydroxylase deficiency correlates with the degree of enzymatic compromise.