In some fields of steroid endocrinology, it has long been accepted that the potency of a hormone may depend not only on its secretion rate and rate of hepatic clearance but also on specific metabolic transformation at the site of the target cell. The crucial role of tissue 5α reductase activity on the action of testosterone is a spectacular example (Peterson, ImperatoMcGinley, Gautier & Sturla, 1977). Curiously—it is easy to be wise after the event—this line of thought seems rarely to have been exercized in explanations of corticosteroid action. Clearly, the severity of diseases of corticosteroid excess, of which Cushing's and Conn's syndromes are the best known examples, is strongly correlated with the secretion rate of cortisol and aldosterone respectively. However, in some forms of hypertension where deranged corticosteroid action might be expected to provide an acceptable explanation (e.g. increased mineralocorticoid secretion in low-renin essential hypertension), no abnormalities of secretion
M Fraser, SG Matthews, G Braems, T Jeffray, and Challis JR
Development of the fetal adrenal gland is crucial not only for maturation of several fetal organ systems and the initiation of parturition, but also for the development of the fetal response to stress. The enkephalin-related peptides are present in the chromaffin cells of the fetal adrenal medulla and are secreted in response to stress and with sympathetic stimulation. However, changes in expression of preproenkephalin (PENK) with gestation and in response to stress have not been studied in detail. Therefore we examined the developmental pattern of PENK gene expression in the adrenal gland of fetal and newborn lambs, and of adult sheep. We also determined whether levels of PENK mRNA in the fetal adrenal gland changed in response to exogenous glucocorticoids in late gestation, or in response to hypoxemia. Adrenal glands were removed from fetal sheep, lambs and adult sheep at different stages of development for measurement of PENK mRNA. Cortisol was infused (5 micrograms/min) for 12, 24 or 96 h beginning on day 124-129 of gestation. Moderate hypoxemia was induced for 48 h beginning on day 126-130, or at day 134-136 of gestation, by lowering the maternal fractional inspired oxygen. At the end of the treatment periods, the ewes and fetuses were euthanized. Adrenal PENK mRNA were measured by Northern blot analysis. PENK mRNA levels in fetal adrenals were significantly higher (P < 0.05) on days 140-141 of gestation than earlier in pregnancy, and then decreased significantly with the onset of parturition (days 142-146). After cortisol infusion to the fetus for 96 h there was a significant reduction in adrenal PENK mRNA levels. Hypoxemia resulted in a significant increase in PENK mRNA levels in fetuses at day 126-130 of gestation, but not at the later time in pregnancy when endogenous plasma cortisol concentrations were higher. We conclude that there is a decrease in levels of PENK mRNA in the fetal adrenal gland before parturition at the time of the endogenous prepartum rise in plasma cortisol. Hypoxemia led to an elevation of PENK mRNA levels in fetuses at less than 130 days, but after that time, when the basal and stimulated cortisol responses had risen, there was no significant effect of hypoxemia on PENK mRNA. Cortisol infusion to the fetus at this stage of pregnancy resulted in a decrease in adrenal PENK mRNA levels. We suggest that cortisol may play an important role in the regulation of fetal adrenal PENK mRNA levels and enkephalin synthesis by the adrenal gland of the fetal sheep.
J. W. GREINER, R. E. KRAMER, and H. D. COLBY
Adrenal cortisol secretion is greater in female than male guinea-pigs and declines with maturation in animals of both sexes. In an attempt to determine the intra-adrenal mechanisms responsible for age and sex influences on corticosteroid output, adrenocortical enzyme activities were compared in sexually immature (3 weeks) and mature (17 weeks) animals. Adrenal mitochondrial protein concentration decreased with maturation in male and female guinea-pigs. 11β-Hydroxylase activity in adrenal mitochondria was also lower in mature than immature guinea-pigs but greater in males than females. Neither mitochondrial cytochrome P-450 concentration nor cholesterol side-chain cleavage activity varied with age or sex. Adrenal microsomal protein concentration and 21-hydroxylase activity were similar in male and female guinea-pigs of the same age but far greater in mature than immature animals. Microsomal cytochrome P-450 concentration was unaffected by age or sex. Adrenal Δ4-steroid (cortisol) hydrogenase activity increased with maturation in both male and female guinea-pigs and was higher in males than females. These observations indicate that cortisol secretion, as modified by age and sex, correlates closely with adrenal steroid reductive but not oxidative metabolism, suggesting that changes in Δ4-hydrogenase activity are responsible, at least in part, for the decline in adrenal secretion during maturation in guinea-pigs.
Ping Ye, Barbara Mariniello, Franco Mantero, Hirotaka Shibata, and William E Rainey
The source of aldosterone in 30–40% of patients with primary hyperaldosteronism (PA) is unilateral aldosterone-producing adenoma (APA). The mechanisms causing elevated aldosterone production in APA are unknown. Herein, we examined the expression of G-protein-coupled receptors (GPCRs) in APA and demonstrated that when compared with normal adrenals, there is a general elevation of certain GPCR in many APA and/or ectopic expression of GPCR in others. RNA samples from normal adrenals (n = 5), APAs (n = 10), and cortisol-producing adenomas (CPAs; n = 13) were used on 15 genomic expression arrays, each of which included 223 GPCR transcripts presented in at least 1 out of 15 of the independent microarrays. The array results were confirmed using real-time RT-PCR (qPCR). Four GPCR transcripts exhibited a statistically significant increase that was greater than threefold when compared with normal adrenals, suggesting a general increase in expression when compared with normal adrenal glands. Four GPCR transcripts exhibited a > 15-fold increase of expression in one or more of the APA samples when compared with normal adrenals. qPCR analysis confirmed array data and found the receptors with the highest fold increase in APA expression to be LH receptor, serotonin receptor 4, GnRH receptor, glutamate receptor metabotropic 3, endothelin receptor type B-like protein, and ACTH receptor. There are also sporadic increased expressions of these genes in the CPAs. Together, these findings suggest a potential role of altered GPCR expression in many cases of PA and provide candidate GPCR for further study.
D. PAULINE ALEXANDER, H. G. BRITTON, V. H. T. JAMES, D. A. NIXON, R. A. PARKER, E. MARELYN WINTOUR, and R. D. WRIGHT
From the left adrenal of ten sheep foetuses and four lambs aged from 110 days after conception to 14 days after birth, adrenal venous blood was collected and assayed for cortisol, corticosterone and aldosterone. These steroids were secreted at all ages but the rate of secretion was greatly increased toward term and after birth. The increase coincided with morphological changes in the adrenal gland. At no stage was the rate significantly increased by corticotrophin, and in two young foetuses it was not decreased by dexamethasone. In two foetuses and one lamb, angiotensin II did not increase the rate of secretion of any of the three steroids significantly, and the blood pressure was raised only in the lamb. It is probable that the secretion of the steroids was maximal under the conditions of the experiments.
D S Gardner, B W M Van Bon, J Dandrea, P J Goddard, S F May, V Wilson, T Stephenson, and M E Symonds
Glucocorticoids are proposed to act as intermediary factors that transcribe the developmental programming sequelae of maternal nutrient restriction (NR). Periconceptional under-nutrition of sheep markedly activates fetal hypothalamic–pituitary–adrenal (HPA) axis activity leading to preterm birth, while transient undernutrition during late gestation in sheep programs adult HPA axis function. To date, no study has examined resting or stimulated HPA axis function in young adult offspring following a periconceptional nutritional challenge. In the present study, 20 ewes were either periconceptionally undernourished (50% metabolisable energy requirements from days 1 to 30 gestation; NR, n = 8) or fed to control levels (100% requirement; controls, n = 12) to term (147 days gestation). Ewes were blood sampled remotely at 2 and 30 days using automated blood sampling equipment. Thereafter, offspring (controls, n = 6/6 males/females; NR, n = 4/4 males/females) were reared to 1 year of age and on separate days received either an i.v. corticotrophin-releasing hormone (CRH; 0.5 μg/kg) and vasopressin (AVP; 0.1 μg/kg) challenge or a synthetic ACTH i.v. bolus (Synacthen; 1.25 μg/kg), and blood samples were taken (manually and remotely) at appropriate intervals for measurement of plasma ACTH and cortisol accordingly. Resting plasma cortisol, assessed remotely, was similar in ewes during undernutrition (control 18.3 ± 1.4 vs NR 23.4 ± 1.9 nmol/l) and in offspring at 4 months of age (control male 17.6 ± 2.9; control female 17.2 ± 0.4, NR male 16.5 ± 3.1, NR female 21.7 ± 4.0 nmol/l). At 12 months of age, however, resting plasma cortisol was significantly increased in NR females (control male 28.0 ± 1.5, control female 32.9 ± 9, NR male 32 ± 7, NR female 53 ± 10 nmol/l, F 5.7, P = 0.02) despite no difference in plasma ACTH concentration. There was an interaction between nutritional group and gender for both the pituitary and adrenal responses to CRH and AVP, i.e. for controls, females exhibited increased plasma ACTH or cortisol relative to males but for NR this trend was either not present or reversed. The adrenocortical response to synthetic ACTH was gender-dependent only, being greater in female offspring. Combined CRH and AVP provoked a transient hypertension and marked bradycardia in all animals, irrespective of dietary group or gender and could be effectively reproduced by an AVP bolus alone. In conclusion, the present study has shown that periconceptional undernutrition of sheep has only a minor influence on HPA axis function in their young adult offspring when considered alongside the effect of gender per se.
A. JOSEPHINE MILNER and I. H. MILLS
Adrenals from foetuses of 13 to 27 weeks gestation were sliced and incubated with 5 μC of [4-14C]progesterone for 2 hr. The biosynthesis of cortisol, 11-deoxycortisol, androstenedione and 11β-hydroxyandrostenedione was estimated by reverse isotope dilution. Cortisol was the major product identified and the production of both cortisol and 11β-hydroxyandrostenedione increased with gestational age in approximate proportion to the increasing adrenal weight. The ratio of (cortisol plus 11-deoxycortisol) to (androstenedione plus 11β-hydroxyandrostenedione) was constant at 13, 16 and 27 weeks gestation. The production of cortisol and androstenedione from progesterone and from pregnenolone by adrenal tissue from a 27-week-old foetus is compared.
P. J. LEONARD
Adrenalectomy in the rat caused an increase of intracellular sodium, both total and relative concentration in heart tissue and a decrease of both in abdominal muscle. These changes were reversed after administration of aldosterone. When aldosterone was given in similar doses to normal animals no changes were observed. It was concluded that an increase in the intracellular sodium concentration of heart and/or other soft tissues, including the adrenals, may stimulate the secretion of aldosterone. A possible regulating system is discussed. It is suggested that total sodium and its intracellular concentration in muscle are influenced by the availability of aldosterone and sodium.
B. S. HETZEL, R. R. McSWINEY, I. H. MILLS, and F. T. G. PRUNTY
1. Aldosterone has been administered by various routes to a patient with normal adrenals and to two patients with Addison's disease. The intramuscular route gave the most regular effect on sodium retention. In some instances intravenous infusion was very effective.
2. In one patient with Addison's disease, aldosterone and cortisone had opposing effects. Aldosterone produced sodium retention, potassium loss and water retention to a significant degree, whereas a single dose of cortisone stimulated a loss of all these substances. The urinary K/Na ratio is a valuable index in assessing aldosterone activity.
3. It was possible to choose conditions, namely presumed adrenocortical hyperactivity and hypertonic saline infusion, where the sodium retaining properties of aldosterone were counteracted.
4. Aldosterone in dosages up to 1 mg was without effect on the sensitivity to insulin in two patients with adrenal insufficiency. Further negative effects, namely on blood eosinophil levels, nitrogen excretion, steroid metabolism and blood sugar levels, were observed.
P. J. LEONARD
Aldosterone secretion is increased in rats on a diet low in sodium content or in rats with nephrosis induced by administration of an aminonucleoside. Distributions of water and sodium in heart, liver, adrenals and abdominal muscle were compared in nephrotic rats, sodium-restricted rats and rats maintained on a normal diet. In nephrotic animals total tissue sodium increased significantly in liver, heart and abdominal muscle and was associated with increased intracellular sodium (both absolute amount and concentration) in these tissues as well as in the adrenals; extracellular sodium decreased in heart and adrenals and increased in abdominal muscle. In nephrotic rats increased total tissue water in liver and abdominal muscle was associated with increased extracellular water while increased total water in adrenals was accompanied by increased intracellular water. The results in sodium-restricted rats were similar to those in nephrotic rats except that no changes were found in abdominal muscle and that water content of liver was unchanged.