Effect of 3-acetylpyridine on the functional activity of the adrenal cortex]

A reduction of blood corticosteroid content was observed in rats blood after the administration of 3-acetylpyridine. The rats given ACTH after 3-acetylpyridine showed a lesser elevation of corticosteroids in the blood and adrenal gland tissue than the intact animals; 3-acetylpyridine diminished the activity of dehydrogenase glucose-6-phosphate in the adrenal glands. The authors suggested that the action of acetylpyridine was realized at the adrenal gland level and consisted in inhibition of the NADP-H2 generation in the dehydrogenase systems.     

Regression of the changes developed in the adrenal cortex in hypercholesterolemia

Administration of cholesterin to rabbits for 2 months results in its increased concentration in blood and in adrenal cortex. Adrenocorticocytes demonstrate a decreased nuclear-cytoplasmic ratio, decreased concentration of protein and RNA in cytoplasm, lowered succinate dehydrogenase and 3 beta-ol-++steroid dehydrogenase activity. In 2 months after abolishing cholesterin, a considerable part of the changes mentioned remains. If during this period dexamethasone, inhibiting the gland activity, is administered, the regression of the changes decelerates. Administration of the adrenal cortex activator--corticotropin--facilitates normalization of most of the parameters, altered in the gland under the effect of cholesterin administration.     

Human adrenal cells that express both 3β-hydroxysteroid dehydrogenase type 2 (HSD3B2) and cytochrome b5 (CYB5A) contribute to adrenal androstenedione production

Androstenedione is one of several weak androgens produced in the human adrenal gland. 3β-Hydroxysteroid dehydrogenase type 2 (HSD3B2) and cytochrome b5 (CYB5A) are both required for androstenedione production. However, previous studies demonstrated the expression of HSD3B2 within the zona glomerulosa (ZG) and fasciculata (ZF) but low levels in the zona reticularis. In contrast, CYB5A expression increases in the zona reticularis (ZR) in human adrenal glands. Although their colocalization has been reported in gonadal theca and Leydig cells this has not been studied in the human adrenal. Therefore, we immonolocalized HSD3B2 and CYB5A in normal human adrenal glands and first demonstrated their co-expression in the cortical cells located at the border between the ZF and ZR in normal human adrenal. Results of in vitro studies using the human adrenal H295R cells treated with the HSD3B2 inhibitor, trilostane, also demonstrated a markedly decreased androstenedione production. Decreasing CYB5A mRNA using its corresponding siRNA also resulted in significant inhibition of androstenedione production in the H295R cells. These findings together indicate that there are a group of cells co-expressing HSD3B2 and CYB5A with hybrid features of both ZF and ZR in human adrenal cortex, and these hybrid cortical cells may play an important role in androstenedione production in human adrenal gland.     

Characterization of the guinea pig 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4-isomerase expressed in the adrenal gland and gonads

The guinea pig adrenal gland, analogous to the human, possesses the capacity to synthesize C(19) steroids. In order to further understand the control of guinea pig adrenal steroidogenesis we undertook the characterization of the guinea pig 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4)-isomerase (3beta-HSD) expressed in the adrenal gland. A cDNA clone encoding guinea pig 3beta-HSD isolated from a guinea pig adrenal library is predicted to encode a protein of 373 amino acid residues and 41,475Da. Ribonuclease protection assay suggests that this cDNA corresponds to the predominant, if not the sole, mRNA species detectable in total RNA from the guinea pig adrenal gland, ovary and testis. The guinea pig 3beta-HSD shows a similar affinity for both pregnenolone and dehydroepiandrosterone, and in addition, a 17beta-HSD type II-like activity was also observed. A phylogenetical analysis of the 3beta-HSD gene family demonstrates that the guinea pig is in a parallel branch to the myomorpha group supporting the hypothesis that the guinea pig lineage has branched off after the divergence among primates, artiodactyls and rodents, suggesting the paraphyly of the order rodentia.     

Adrenal 11-beta hydroxysteroid dehydrogenase activity in response to stress

This work studied the effect of stresses produced by simulated gavage or gavage with 200 mmol/L HCl two hours before adrenal extraction, on the activities of the 11beta-hydroxysteroid dehydrogenase 1 and 11beta-hydroxysteroid dehydrogenase 2 isoforms present in the rat adrenal gland. These activities were determined on immediately prepared adrenal microsomes following incubations with 3H-corticosterone and NAD+ or NADP+. 11-dehydrocorticosterone was measured as an end-product by TLC, and controls were adrenal microsomes from rats kept under basal (unstressed) conditions. 11beta-hydroxysteroid dehydrogenase 1 activity, but not 11beta-hydroxysteroid dehydrogenase 2 activity, was increased under both stress-conditions. Homeostatically, the stimulation of 11beta-hydroxysteroid dehydrogenase 1 activity would increase the supply of glucocorticoids. These, in turn, would activate the enzyme phenylethanolamine N-methyl transferase, thereby improving the synthesis of epinephrine as part of the stress-response.     

Enzymic changes in rabbit and rat mammary gland during the lactation cycle

1. Activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), isocitrate dehydrogenase (EC 1.1.1.42), malate dehydrogenase (EC 1.1.1.37), malate dehydrogenase (decarboxylating) (EC 1.1.1.40), and pyruvate carboxylase (EC 6.4.1.1) were determined in subcellular fractions of mammary gland from rabbits during pregnancy, at different stages of lactation and during weaning. The results were compared with those obtained in similar experiments with rat mammary gland. 2. Three bases of expression of the activity of enzymes in the particle-free supernatant fraction of mammary gland were compared. During lactation, activity expressed per mg. of particle-free supernatant protein (uncorrected for milk protein) correlated well with that expressed per mug. of DNA phosphorus. The disadvantages of expressing activities per g. wet wt. are discussed. 3. The major differences between the two tissues were: (a) neither malate dehydrogenase (decarboxylating) nor a soluble form of pyruvate carboxylase could be detected in rabbit mammary gland at any stage of the lactation cycle; (b) isocitrate dehydrogenase increased in activity during lactation in rabbit mammary gland, but not in that of the rat. 4. Pyruvate carboxylase in the mitochondrial fraction of rabbit mammary gland, and in both the mitochondrial and the soluble fractions of rat mammary gland, did not change in activity during lactation. 5. For each tissue, the NADP-dependent dehydrogenases studied had a high activity at all stages of the lactation cycle compared with the rate of fatty acid synthesis at mid-lactation. The significance of these results is discussed with respect to the supply of NADPH via NADH.     

IGF1 and 2 in two models of adrenal growth

Insulin-like growth factors (IGFs) 1 and 2 were measured in the adrenal glands of rats undergoing either compensatory growth following left unilateral adrenalectomy or adrenal regeneration following bilateral adrenal enucleation. In normal rat adrenal gland, the tissue concentration of IGF2 (7.45 +/- 0.99 pg/micrograms protein) wa higher than IGF1 (1.26 +/- 0.23 pg/micrograms protein), both peptides being more abundant in the inner zones of the adrenal gland compared to the capsule-glomerulosa. During compensatory growth of the right adrenal gland, IGF1 and 2 increased significantly compared with control right adrenal glands at 24 h following left unilateral adrenalectomy (P less than 0.001). At 68 h, the increase remained significant for IGF1 (P = 0.012). The two peptides were measured in the regenerating adrenal gland at 7, 14 and 21 days following bilateral enucleation. Whilst there was a trend towards an increase in the IGF1 and 2 content of regenerating adrenal glands, the increase was significant only for IGF2 in the left adrenal gland at 21 days following enucleation. Plasma IGF1 and 2 did not increase compared to controls during the experiments (110.97 +/- 1.95 and 46.33 ng/ml, respectively), suggesting that the changes in tissue IGF reflect increased local production during rapid growth of the adrenal gland.     

Histochemical study on adrenal delta 5-3 beta-hydroxysteroid dehydrogenase activity in cadmium treated toad (Bufo melanostictus).

Effect of a single subcutaneous injection of cadmium chloride at the dose of 0.5 mg/toad on adrenal delta 5-3 beta-hydroxysteroid dehydrogenase (delta 5-3 beta-HSD) was observed after 7 days. The activity of delta 5-3 beta-HSD was measured histochemically. The experiments indicate that cadmium chloride resulted in a significant decrease in the activity of adrenal delta 5-3 beta-HSD in toad during breeding season (June-July).     

模拟高原低氧对新生大鼠肾上腺皮质功能发育的影晌

本文探讨新生大鼠肾上腺皮质对高原低氧的应答及模拟高原低氧对其功能发育的影响。结果表明,当不同日龄大鼠暴露于５ｋｍ及７ｋｍ海拔２４ｈ,７ｄ、１４ｄ龄大鼠肾上腺皮质无明显应答反应。２１ｄ及２８ｄ龄大鼠肾上腺皮质酮水平随海拔增高而增加,血浆皮质酮表现为抑制作用。当１ｄ龄新生大鼠在５ｋｍ海拔高度发育３ｄ和７ｄ,其肾上腺皮质功能无异于正常发育大鼠;但发育１４ｄ、２１ｄ及２８ｄ,其血液及肾上腺中皮质酮含量均明显低于对照组,肾上腺皮质功能发育严重受抑     

Relationship between apolipoprotein E mRNA expression and tissue cholesterol content in rat adrenal gland.

Among extrahepatic tissues the adrenal gland has one of the highest concentrations of apoE mRNA and the highest rate of apoE synthesis. In the present investigation several previously described in vivo treatments were used to assess the relationship between apoE expression and cellular cholesterol in the rat adrenal gland. Treatment of rats with 4-aminopyrazolo[3,4-d]pyrimidine (4-APP) to lower serum cholesterol concentration and deplete adrenal gland cholesterol content decreased adrenal gland apoE mRNA concentration. These adrenal responses were blocked by dexamethasone (DEX) suggesting that the effect of 4-APP occurred indirectly via stimulation of the adrenal gland by endogenous adrenocorticotrophic (ACTH). Relative to control rats, DEX treatment increased both adrenal gland cholesterol content and apoE mRNA concentration. Concurrent ACTH and DEX administration reduced both adrenal gland cholesterol content and apoE mRNA concentration relative to DEX-treated rats. ACTH administration also rapidly decreased adrenal gland apoE mRNA concentration and cholesterol content in rats pretreated with DEX. In all the above experiments, adrenal gland cholesterol content and apoE mRNA concentration were positively correlated (r = 0.78, P = 0.0001). In contrast, aminoglutethimide treatment, which blocks adrenal gland steroidogenesis and greatly increases adrenal gland cholesterol content, was without effect on apoE mRNA concentration. ACTH administration to rats treated with DEX + aminoglutethimide resulted in decreased adrenal apoE mRNA despite greatly increased adrenal cholesterol content. This uncoupling of adrenal gland cholesterol content and apoE mRNA concentration suggests that apoE mRNA expression and cellular cholesterol are regulated independently by ACTH.     

Molecular biology of 11β-hydroxylase and 11β-hydroxysteroid dehydrogenase enzymes

There are two steroid 11β-hydroxylase isozymes encoded by the CYP11B1 and CYP11B2 genes on human chromosome 8q. The first is expressed at high levels in the normal adrenal gland, has 11β-hydroxylase activity and is regulated by ACTH. Mutations in the corresponding gene cause congenital adrenal hyperplasia due to 11β-hydroxylase deficiency; thus, this isozyme is required for cortisol biosynthesis. The second isozyme is expressed at low levels in the normal adrenal gland but at higher levels in aldosterone-secreting tumors, and has 11β-hydroxylase, 18-hydroxylase and 18-oxidase activities. The corresponding gene is regulated by angiotensin II, and mutations in this gene are found in persons who are unable to synthesize aldosterone due to corticosterone methyloxidase II deficiency. Thus, this isozyme is required for aldosterone biosynthesis.

Cortisol and aldosterone are both effective ligands of the “mineralocorticoid” receptor in vitro, but only aldosterone is a potent mineralocorticoid in vivo. This apparent specificity occurs because 11β-hydroxysteroid dehydrogenase in the kidney converts cortisol to cortisone, which is not a ligand for the receptor. This enzyme is a “short-chain” dehydrogenase which is encoded by a single gene on human chromosome 1. It is possible that mutations in this gene cause a form of childhood hypertension called apparent mineralocorticoid excess, in which the mineralocorticoid receptor is not protected from high concentrations of cortisol.     

The dynamic morphofunctional state of the adrenals in irradiated recipients following bone marrow transplantation

The influence of syngenic bone marrow transplantation in the dose of 1.10(7) cell/ml upon the adrenal gland state of lethally irradiated recipients at various stages of posttransplantation period during 3 months has been studied at 150 linear F1 (CBA x C57B) male mice. Histological and histochemical studies conducted have shown the transplantation of native and cryopreserved bone marrow of the lethally irradiated recipients to result, depending upon observation time, in undulating change in adrenal gland weight, cortex thickness and lipid content in spongiocytes, which testifies to the certain dynamics of processes, occurring in recipients' adrenal gland.     

Response of adrenal 3beta-hydroxy-delta5-steroid dehydrogenase to adrenocorticotropin treatment in thiouracil-fed male mice

A number of parallels can be drawn between the reported endocrine status of thiouracil-fed young rodents and that of aged animals, particularly with regard to the hypothalamus-pituitary-adrenal axis. Since the activity of the adrenal steroidogenic enzyme 3beta-hydroxy-delta5-steroid dehydrogenase (3beta-HSD) has been shown to be depressed in aged rats and mice, the present study was done to determine whether exposure of young mice to thiouracil had a similar effect on adrenal 3beta-HSD activity. Feeding the goitrogen thiouracil at 0.25% (w/w) of the maternal diet from conception, and keeping it 0.25% of the offsprings' diet after weaning, significantly elevated activity of 3beta-HSD per gram of adrenal gland above control levels in 4-month-old mice, perhaps to compensate for depressed adrenal mass. Daily subcutaneous injections of physiological saline (0.9%) for 4 days was sufficient to increase 3beta-HSD activity per gram of adrenal tissue in euthyroid (P less than 0.05) but not in thiouracil-fed mice. Subcutaneous administration of ACTH (2 IU daily for 4 days) significantly increased adrenal 3beta-HSD activity to comparable levels in thiouracil-fed and euthyroid animals. Thus, thiouracil enhances the activity of 3beta-HSD per gram of adrenal tissue and does not prevent response of enzyme activity to exogenous ACTH.     

Liver X receptors regulate adrenal steroidogenesis and hypothalamic-pituitary-adrenal feedback

The nuclear hormone receptors liver X receptor alpha (LXRalpha) (NR1H3) and LXRbeta (NR1H2) are established regulators of cholesterol, lipid, and glucose metabolism and are attractive drug targets for the treatment of diabetes and cardiovascular disease. Adrenal steroid hormones including glucocorticoids and mineralocorticoids are known to interfere with glucose metabolism, insulin signaling, and blood pressure regulation. Here we present genome-wide expression profiles of LXR-responsive genes in both the adrenal and the pituitary gland. LXR activation in cultured adrenal cells inhibited expression of multiple steroidogenic genes and consequently decreased adrenal steroid hormone production. In addition, LXR agonist treatment elevated ACTH mRNA expression and hormone secretion from pituitary cells both in vitro and in vivo. Reduced expression of the glucocortioid-activating enzyme 11beta-hydroxysteroid dehydrogenase 1 in pituitary cells upon LXR activation suggests blunting of the negative feedback of glucocorticoids by LXRs. In conclusion, LXRs independently interfere with the hypothalamic-pituitary-adrenal axis regulation at the level of the pituitary and the adrenal gland.     

Functional role of local angiotensin-converting enzyme (ACE) in adrenal catecholamine secretion in vivo

The aim of the present study was to investigate whether exogenous angiotensin I (AngI) is locally converted to angiotensin II (AngII), which in turn results in an increase in the adrenal catecholamine (CA) secretion in the adrenal gland in anesthetized dogs. Plasma CA concentrations in adrenal venous and aortic blood were determined by an HPLC-electrochemical method. Adrenal venous blood flow was measured by gravimetry. Local administration of AngI (0.0062 to 6.2 microg, 0.0096 to 9.6 microM) to the left adrenal gland resulted in significant increases in CA output in a dose-dependent manner. Following administration of 0.62 microg (0.96 microM) of AngI, adrenal epinephrine and norepinephrine outputs increased from 20.8+/-13.6 to 250.9+/-96.4 ng x min(-1) x g(-1) (p<0.05, n = 5) and from 2.8+/-1.7 to 29.6+/-11.1 ng x min(-1) x g(-1) (p<0.05, n = 5), respectively. From the same left adrenal gland, the output of AngII increased from -0.02+/-0.04 to 26.39+/-11.38 ng x min(-1) x g(-1) (p<0.05, n = 5), while plasma concentrations of AngII in aortic blood remained unchanged. In dogs receiving captopril (12.5 microg, 0.5 mM) 10 min prior to AngI, the net amounts of CA and AngII secreted during the first 3 min after AngI were diminished by about 80% (p<0.05, n = 5) compared with those obtained from the control group. There was a close correlation (r2 = 0.91, n = 6) between the net increases in AngII and CA outputs induced by AngI. The results indicate that the local angiotensin converting enzyme is functionally involved in regional AngII formation in the canine adrenal gland in vivo. The study suggests that AngII thus generated may play a role in the local regulation of adrenal CA secretion.     

Source and regulation of 17 alpha-hydroxyprogesterone during baboon pregnancy

The present study determined the source and regulation of 17 alpha-hydroxyprogesterone (17-OHP4) during mid-late baboon pregnancy. Serum 17-OHP4 (ng/ml) in 5 untreated baboons increased from low values at mid-late gestation to a mean (+/- SEM) of 0.49 +/- 0.02 during the final 20 days of gestation. Fetectomy of 5 baboons resulted in serum 17-OHP4 concentrations which declined to and remained at baseline. Serum 17-OHP4 concentrations were 5- to 10-fold greater (P less than 0.001) in the uterine, utero-ovarian, and umbilical veins than peripherally. Apparently the fetal adrenal provides precursors for placental 17-OHP4 formation because the fetal adrenal gland develops delta 5-3 beta-hydroxysteroid dehydrogenase only late in gestation, and because the fetal adrenal and not the placenta has the capacity for 17-hydroxylation. Thus, at mid-late gestation the placenta appears to supply a major, and at term the corpus luteum a minor portion of the total 17-OHP4. Administration of the estrogen antagonist ethamoxytriphetol (MER-25, 15 mg/kg BW) to 4 baboons did not affect 17-OHP4 during mid-late gestation, when the placenta was the only source of 17-OHP4. However, MER-25 resulted in serum 17-OHP4 concentrations (ng/ml) at term which were greater (1.08 +/- 0.10, P less than 0.001) than in untreated baboons (0.49 +/- 0.02). Prior removal of the corpus luteum of pregnancy in 4 animals subsequently given MER-25 prevented this rise in 17-OHP4. This suggests that the marked elevation in 17-OHP4 observed near term after MER-25 administration was of luteal origin and that antiestrogen enhanced 17-OHP4 secretion by the corpus luteum.     

Extraglandular hormonal steroidogenesis in aged rats

We have examined the metabolism in vitro of [4-¹⁴C]pregnenolone by the following organs of 2.4-year-old rats: submandibular gland, stomach, duodenum, liver, lung, heart, spleen, kidney, skin, prostate, testis and adrenal. All tissues converted pregnenolone to progesterone, the highest yields being observed with adrenal, testis and skin. Androgen formation was intense in the testis and absent in the adrenal. Moreover, 17-hydroxylation of pregnenolone occurred moderately in kidney, skin and submandibular gland and markedly in duodenum and stomach, which also produced high amounts of dehydroepiandrosterone and/or 5-androstene-3β,17β-diol. Extratesticular synthesis of androstenedione and testosterone was very low. A significant formation of 20-dihydropregnenolone was observed in all tissues but stomach, duodenum and steroidogenic endocrines. Corticosteroids were not synthesized extraadrenally, except a small amount of 11-deoxycorticosterone in the testis. These results indicate that key steroid-biosynthetic enzymes, such as 3β-hydroxysteroid dehydrogenase/Δ⁵′Δ⁴ isomerase, 17β- and 20-hydroxysteroid dehydrogenases and steroid 17-monooxygenase/17,20-lyase are also expressed extraglandularly in the rat.