Secretion of 6beta-hydroxycortisol by normal human adrenals and adrenocortical adenomas

Although 6beta-hydroxycortisol (6betaOHF) is usually considered a cortisol metabolite produced by the liver, a few reports suggest that it may also originate from extrahepatic sources. To examine whether human adrenal cells are capable of 6beta-hydroxylating cortisol, we measured 6betaOHF secretion with a radioimmunoassay method in isolated human adrenal cell systems obtained from three normal adrenals, four nonhyperfunctioning adrenocortical adenomas, two adrenal adenomas causing Cushing's syndrome, and five aldosterone (Aldo)-producing adenomas. Cells were examined both under basal conditions and after stimulation with adrenocorticotrophic hormone (ACTH). In addition, 6betaOHF concentrations were determined in inferior vena cava and suprarenal vein plasma samples obtained from the side of nonhyperfunctioning adrenal adenomas (five patients) and aldosterone-producing adenomas (five patients). Under basal incubation conditions, 6betaOHF secretion, expressed as a percent of cortisol secretion, was between 0.5 and 2.0% in normal adrenal cells, between 1.0 and 7% in cells from nonhyperfunctioning adenomas, 12 and 15% in cells from Cushing's syndrome patients, and between 2.6 and 3.9% in cells from aldosterone-producing adenomas. In these cells, increasing doses of ACTH produced a dose-dependent stimulation of both 6betaOHF and cortisol secretion. The 6betaOHF concentration in suprarenal vein samples obtained from the side of adenomas was markedly increased; the suprarenal vein/inferior vena cava 6betaOHF ratios were 13.1+/-2.1 (mean+/-S.E.) in the case of nonhyperfunctioning adenomas and 17.8+/-4.5 in the case of aldosterone-producing adenomas. These results firmly suggest that 6betaOHF is not only a hepatic metabolite, but also a secretory product of human adrenals and that similarly to cortisol, its secretion may be controlled by ACTH.     

Studies on lipoprotein and adrenal steroidogenesis: II. Utilization of low density lipoprotein- and high density lipoprotein-cholesterol for steroid production in functioning human adrenocortical adenoma cells in culture

We examined the utilization of human low density lipoprotein (LDL)- and high density lipoprotein (HDL)-cholesterol for steroid production in primary monolayer culture cells from adenomas of primary aldosteronism and Cushing's syndrome and an adrenal of nodular hyperplasia of Cushing's syndrome. We compared the data obtained with findings in the case of cultured normal human adrenocortical cells. In the presence of 10(-7) M adrenocorticotropin (ACTH), the addition of either LDL or HDL to the culture medium at a cholesterol concentration of 100 micrograms/ml led to a significant increase in the daily secretion rates of cortisol, dehydroepiandrosterone sulfate (DHEA-S) and aldosterone in the adenoma and nodular hyperplasia cells, as in the normal cells. Although LDL greatly increased the secretion of steroid hormones, no significant difference in steroid secretion following the treatments with LDL and HDL were observed in these cultured cells. The contribution of endogenous cholesterol to steroid production was also high, thereby indicating that the neoplastic transformation did not have untoward effects. Cells from adenomas of primary aldosteronism secreted not only aldosterone, but also cortisol and DHEA-S. The daily secretion rates of these steroids were markedly increased when ACTH was added to the medium. With prolonged exposure to ACTH, however, the rate of aldosterone secretion showed a gradual decrease with the incubation time. This decrease might be due to the impaired conversion of corticosterone to 18-hydroxycorticosterone. In case of adenomas in patients with Cushing's syndrome, the secretion of steroid hormones varied in quantity and quality, depending on the type of plasma cortisol response to the rapid ACTH test in vivo, thereby suggesting that the adrenocortical adenoma of Cushing's syndrome might be divided into two subtypes. These results indicate that human functioning adrenocortical adenoma cells utilize plasma lipoproteins as a source of cholesterol for steroidogenesis during the prolonged stimulation of steroid secretion.     

Differential redistribution of protein kinase C in human aldosteronoma cells and adjacent adrenal cells stimulated with ACTH and angiotensin II

We have examined protein kinase C activity and hormone secretion in aldosteronoma cells derived from adrenocortical glomerulosa cells and in adjacent adrenal cells containing adrenocortical fasciculata-reticularis cells. When aldosteronoma cells were stimulated with ACTH or angiotensin II, protein kinase C activity gradually decreased in cytosol whereas it increased in membrane. Coincident with the changes of protein kinase C activity, there was enhancement of secretion of aldosterone. On the other hand, incubation of adjacent adrenal fasciculata-reticularis cells with ACTH induced cortisol secretion and an increase in cytosolic protein kinase C activity, accompanied by a decrease in the enzyme activity in membrane. Upon stimulation with angiotensin II, adjacent adrenal fasciculata-reticularis cells did not secrete cortisol and no significant changes of protein kinase C activities were observed in either cytosolic or membrane fractions. These results indicate that both ACTH and angiotensin II stimulate aldosterone secretion and cause translocation of protein kinase C from cytosol to membranes in aldosteronoma cells, whereas, in fasciculata-reticularis cells, only ACTH stimulates cortisol secretion and this is associated with translocation of protein kinase C in the opposite direction, viz., from membrane to cytosol.     

Mild adrenal 3 beta-hydroxysteroid dehydrogenase deficiency with hyperaldosteronism

The patient was admitted to our hospital at 19 and again at 22-yr of age for hirsutism and hypertension. Her baseline and ACTH-stimulated plasma 17-hydroxy pregnenolone, dehydroepiandrosterone and dehydroepiandrosterone sulfate were increased whereas plasma 17-hydroxy progesterone and androstenedione were normal and responded poorly to ACTH. Plasma deoxycorticosterone, corticosterone and cortisol baseline levels were normal, and they responded normally to ACTH. The plasma aldosterone concentration (PAC) was always high and responded well to ACTH, angiotensin III and furosemide-upright stimulation. However, plasma renin activity (PRA) was normal or slightly high, and responded normally to furosemide-upright stimulation and fluorohydrocortisone suppression. Dexamethasone (2 mg/day) for 1-2 weeks suppressed the androgens, cortisol and corticosterone levels. PRA and PAC were suppressed temporally, but PRA returned to normal and PAC to be a high level after 2 weeks of dexamethasone administration. Blood pressure was also reduced temporally but returned to a high level after 2 weeks of dexamethasone. These results indicate that primary aldosteronism and dexamethasone-suppressible hyperaldosteronism were not likely to be present, and unknown aldosterone stimulating factors which potentiated the action of endogenous angiotensin II or ACTH might be responsible for the hyperaldosteronism in this patient. We conclude that this patient had a mild and non-salt losing 3 beta-HSD deficiency in the zona reticularis with normal fasciculata and high glomerulosa function.     

In vitro secretion of ACTH, beta-endorphin and beta-lipotropin in Cushing's disease and Nelson's syndrome

Tissue from histologically confirmed ACTH cell adenomas in Cushing's disease (CD) and Nelson's syndrome (NS) was gained by transsphenoidal surgery. Combined enzymatic and mechanic agitation of tumor tissue yielded a cell suspension. Aliquots of the cell suspension were transferred to superfusion chambers immediately after isolation and investigated for ACTH and beta-endorphin production. Feedback action of cortisol (CO) and dexamethasone on basal hormone production and on lysine vasopressin (LVP) induced ACTH secretion were studied. Adenomatous tissue and anterior lobe tissue from the same patient in CD could be investigated simultaneously in 4 cases. The paraadenomatous tissue showed depression of basal and LVP-induced ACTH secretion. In all adenomatous tissues investigated there was missing or reduced suppression of basal ACTH secretion by physiological levels of CO. CO not only failed to suppress LVP-induced ACTH secretion but also seemed to enhance LVP stimulation in some experiments. This study confirms former results, that a missing or inversed feedback action or glucocorticoids in adenoma cells is a mechanism involved in the pathological ACTH secretion in CD and NS. Bioassayable and immunoreactive ACTH from media of superfusion and short-term static incubation were compared with beta-endorphin and beta-LPH in an assay detecting these two peptides with equimolar sensitivity. Secretory patterns were basically parallel but great differences showed in quantities of hormones secreted. In addition, Sephadex G-50 gel chromatography was performed to separate beta-endorphin from beta-LPH and to calculate the ratios. These profiles show great variations between different adenomas.     

Aldosterone biosynthesis induced by ACTH and angiotensin II in newborn rat adrenocortical cells transfected by c-EJ-Ha-ras oncogene.

Adrenocortical cells were obtained by fractionated trypsination of newborn rat adrenal glands and transfected with a plasmid containing the EJ/T24-Ha-ras oncogene. Isolation of adhesive cells led to a proliferative cell line with an overexpression of 21 kDa ras protein. These cells incubated with corticosterone or deoxycorticosterone as the precursor produced a high level of 18-hydroxycorticosterone and aldosterone as identified by gas chromatography- mass spectrometry. ACTH and angiotensin II increased the basal production of aldosterone nineteen-fold and six-fold respectively. Under ACTH stimulation the ratio between aldosterone and 18-hydroxycorticosterone production was 1:3. The transformation of corticosterone under angiotensin II stimulation yielded up to 41% of 18-hydroxycorticosterone (4.7 micrograms/mg of cell protein per 24h) and 4.4% of aldosterone (0.5 microgram/mg of cell protein per 24h) in a low potassium concentration medium (6 mmol/l). To our knowledge this is the first report of continuous proliferative adrenocortical cells producing aldosterone.     

Reversible hyporeninemic hypoaldosteronism in a patient with tetraplegia

A 66-year-old man with tetraplegia developed hyperkalemia. Hyporeninemic hypoaldosteronism was disclosed on the basis of a lack of response of plasma renin activity to furosemide administration or tilting with marked hypotension and a subnormal response of aldosterone to furosemide stimulation, tilting, angiotensin II infusion and ACTH administration, as well as increased vascular responsiveness to angiotensin II infusion. Of interest was the finding that urinary excretion of epinephrine and norepinephrine was markedly reduced, indicating that hyporeninemia may possibly be due to a chronic lack of sympathetic nervous stimuli. The patient was treated with sodium polystyrene sulfonate resin and/or 9-alpha-fluorohydrocortisone, and wheelchair rehabilitation. However, even after stopping 8-month-mineralcorticoid replacement, normokalemia was maintained. Reexamination of the renin-angiotensin-aldosterone system revealed a normalized response to tilting or ACTH administration along with the normal catecholamine excretion. One more point to be noted is that ACTH administration resulted in a rise in the plasma levels of cortisol, corticosterone and 18-OH-corticosterone, but not aldosterone. This may be attributed to ACTH-stimulated 18-OH-corticosterone derived from the zona fasciculata or alternatively to a partial defect of corticosterone methyl oxidase type II (18-dehydrogenase) in the adrenal glomerulosa cells. These results suggested that hyporeninemic hypoaldosteronism may have been attributable to a decrease in systemic nervous stimuli and that such abnormalities were reversible.     

Steroidogenesis in human aldosterone-secreting adenomas and adrenal hyperplasias: effects of hypoxia in vitro

The synthesis of adrenal steroids requires molecular oxygen. Because arterial hypoxemia is a common clinical condition, the purpose of the present study was to examine steroidogenesis in vitro under physiological changes in O(2) tension (Po(2)) in cells from human adrenal glands with aldosterone-secreting adenomas (ASA; n=3) or with bilateral adrenal hyperplasia causing Cushing's syndrome (n=4). A decrease in Po(2) from 150 mmHg (mild hyperoxia) to 80 mmHg had minimal effect on steroid production. A reduction to 40 mmHg (still well within the physiological range) significantly inhibited cAMP- and ACTH-stimulated aldosterone, cortisol, and dehydroepiandrosterone (DHEA) production from ASA. Furthermore, cortisol and DHEA production in cells from histologically normal tissue, adjacent to ASA and from bilateral adrenal hyperplasias, was also inhibited under a Po(2) of 40 mmHg. We conclude that physiological decreases in Po(2) to levels typical for adrenal venous Po(2) under mild hypoxia inhibit steroidogenesis. These studies may have implications for oxygen therapy in critically ill patients with functional adrenal insufficiency, as well as for therapeutic options in patients with adrenal neoplasms.     

Plasma renin activity and urinary aldosterone in Cushing's syndrome.

The renin-angiotensin-aldosterone system has been evaluated in 19 patients with Cushing's syndrome due to bilateral adrenal hyperplasia and in 2 patients with unilateral adenoma. In the first group urinary aldosterone was within the normal limits with a mean of 8.3 +/- 1.86 microgram/24 h. Aldosterone excretion did not change significantly after furosemide administration, ACTH infusion or dexamethasone. Upright PRA was suppressed in 9/16 patients with a mean of 4.9 +/- 1.85 ng/ml/3 h and showed only a slight response to furosemide. Dexamethasone alone did not produce any change. Both aldosterone and PRA were to some extent stimulated by an association of dexamethasone and furosemide. In the 2 patients with adenoma, aldosterone excretion was also normal, but PRA was very elevated. From our data it is concluded that in Cushing's syndrome due to bilateral hyperplasia, PRA and aldosterone excretion are partially suppressed. From our results on plasma deoxycorticosterone and corticosterone concentration it seems unlikely that these mineralocorticoids are the major cause of this phenomenon. However, it may not be excluded that other yet unidentified hormones could play some role in the pathogenesis of hypertension and renin suppression in Cushing's syndrome.     

Plasma and salivary 6beta-hydroxycortisol measurements for assessing adrenocortical activity in patients with adrenocortical adenomas.

The aim of this study was to examine and compare the potential usefulness of plasma and salivary 6beta-hydroxycortisol measurements for assessing adrenocortical activity in patients with adrenocortical adenomas. Plasma and salivary cortisol as well as 6beta-hydroxycortisol determinations were performed by radioimmunoassay after extraction with ethyl acetate followed by chromatographic separation using a modified paper chromatographic system. Samples were obtained from 36 control subjects and 37 patients with non-hyperfunctioning adrenocortical adenomas in the morning at 8 a.m. after a low-dose of dexamethasone and after stimulation with synthetic depot ACTH. Basal and post-dexamethasone hormone levels were also measured in plasma and salivary samples of 4 patients with Cushing's syndrome from adrenal adenomas. In the baseline state, patients with non-hyperfunctioning adrenocortical adenomas had significantly higher plasma and salivary 6beta-hydroxycortisol levels (mean+/-SE, 79.0+/-7 and 17.1+/-2.2 ng/dl, respectively) compared to those measured in controls (62.0+/-4 and 7.7+/-0.6 ng/dl, respectively), whereas baseline plasma and salivary cortisol levels (9.6+/-0.5 microg/dl and 342+/-39 ng/dl, respectively) were similar to those measured in the control group (9.9+/-0.4 microg/dl and 366+/-24 ng/dl, respectively). In all groups, the changes in plasma and salivary 6beta-hydroxycortisol concentrations after dexamethasone suppression and ACTH stimulation were similar to the changes in plasma and salivary cortisol levels, although the differing ratios of 6betaOHF to cortisol indicated potentially important variations in the induction of 6beta-hydroxylase activity between the three groups. In patients with Cushing's syndrome, baseline plasma and salivary 6beta-hydroxycortisol concentrations (754+/-444 and 104+/-88 ng/dl, respectively) were more markedly increased than plasma and salivary cortisol levels (24.8+/-6.7 microg/dl and 1100+/-184 ng/dl, respectively), and all remained non-suppressible after dexamethasone administration. These results suggests that plasma and salivary 6beta-hydroxycortisol determinations may precisely detect not only overt increases of cortisol secretion in patients with Cushing's syndrome but also mild glucocorticoid overproduction presumably present in patients with non-hyperfunctioning adrenocortical tumors.     

Evidence that corticosterone is not an obligatory intermediate in aldosterone biosynthesis in the rat adrenal

CGS 16949A is a potent inhibitor of aromatase in vitro with an IC50 of 0.03 microM for the inhibition of LH-stimulated estrogen biosynthesis in hamster ovaries. In vivo, CGS 16949A leads to sequelae of estrogen deprivation (e.g. regression of DMBA-induced mammary tumors) without causing adrenal hypertrophy in adult rats. To complement these in vitro and in vivo findings, the effect of CGS 16949A on adrenal steroid biosynthesis in rats was investigated in vitro and in vivo. The surprising finding in vitro was that CGS 16949A inhibited aldosterone biosynthesis (IC50 = 1 microM) at concentrations 100 times lower than those for inhibition of corticosterone biosynthesis (IC50 = 100 microM). Moreover, deoxycorticosterone (DOC) concentrations were elevated at all concentrations of CGS 16949A which inhibited aldosterone synthesis. The classical biosynthetic pathway for aldosterone is DOC----corticosterone----18-OH-corticosterone----aldosterone. Thus inhibition of aldosterone biosynthesis, reflected in DOC accumulation, without affecting corticosterone concentrations, indicates that corticosterone is not an obligatory intermediate in the conversion of DOC to aldosterone in the rat. In vivo, CGS 16949A showed a suppression of plasma aldosterone in ACTH-stimulated male rats at doses which did not significantly affect plasma corticosterone. In conclusion, aldosterone measured both in vitro and in vivo must be derived primarily from a biosynthetic pathway in which corticosterone is not obligatory intermediate.     

Exogenous steroids alter steroidogenesis in cultured Y-1 adrenal tumor cells by actions preceding cyclic AMP

Using cultured Y-1 mouse adrenal tumor cells which produce 20 alpha-hydroxy-4-pregnen-3-one (20-DHP), it was found that 0.01 mM corticosterone and deoxycorticosterone increased basal and inhibited ACTH-induced 20-DHP production during consecutive 30 and 120 min incubations. Steroid effects were concentration-dependent and reversible. Six other steroids tested did not stimulate 20-DHP production and varied in ability to inhibit ACTH-stimulated steroidogenesis. Experiments demonstrated that 20-DHP production following treatment with cholera toxin, N,0'-dibutyryl cyclic AMP (dbcAMP), or pregnenolone was not inhibited by exogenous steroids. Corticosterone (0.01 mM) increased basal and inhibited ACTH-induced intracellular cyclic AMP (cAMP) production. Cytochalasin D, a microfilament perturbing agent, inhibited steroid-stimulated 20-DHP production, suggesting that ACTH and steroid stimulation mechanisms were similar. These findings taken together suggest that exogenous steroids can alter steroidogenesis by modifying plasma membrane adenylate cyclase activity.     

Steroid biosynthesis by zona glomerulosa-fasciculata cells in primary culture of guinea-pig adrenals

Steroidogenesis was studied in guinea-pig glomerulosa-fasciculata cells maintained in primary culture for up to 7 days. The basal secretion which remained stable for the first 2 days in culture rapidly rose to reach a plateau on day 4 at levels 6-7-fold higher than those observed during the first 2 days of culture while the maximal response to ACTH in terms of cortisol and androstenedione secretion was fairly stable throughout the 7-day period. Exposure of glomerulosa-fasciculata cells to ACTH caused a stimulation of pregnenolone, 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone, corticosterone, 11-deoxy-corticosterone, 11-deoxycortisol, cortisol, dehydroepiandrosterone, androstenedione, 11 beta-hydroxyandrostenedione and aldosterone while, after 48 h of incubation, a marked accumulation of end-products, namely cortisol and 11 beta-hydroxyandrostenedione, was observed. The half-maximal steroidogenic response to ACTH occurred at concentrations varying between 1.7 x 10(-11) and 1.1 x 10(-10) mol/l for the 12 steroids examined. Addition of 8-bromoadenosine 3', 5'-cyclic monophosphate stimulated steroid secretion in a dose-dependent manner. Maximal response to 8-bromoadenosine 3', 5'-cyclic monophosphate was obtained at 1 mmol/l, and no further rise of steroid secretion was observed after addition of ACTH. Incubation of glomerulosa-fasciculata cells with labeled corticosterone, cortisol and androstenedione indicates that only androstenedione can be converted into 11 beta-hydroxyandrostenedione, thus suggesting that this end-product is a good parameter of the C-19 steroid production by guinea-pig glomerulosa-fasciculata cells in primary culture. The present data confirm that guinea-pig glomerulosa-fasciculata cells in primary culture provide an interesting model for the study of the regulation of C-19 steroid formation by the adrenals.     

Sex-dependent effect of melatonin on the secretory activity of rat and hamster adrenal gland in vitro

Adrenal quarters from adult male or female hamsters were incubated in the presence of melatonin (10(-7) or 10(-4)M), and cortisol concentration in the incubation medium was assayed by RIA. Melatonin did not change cortisol output by adrenals obtained from the male hamsters, while a slight stimulatory effect was observed in female glands, the lower concentration of melatonin being more effective than the higher one. At both concentrations tested, melatonin notably stimulated corticosterone output by isolated rat adrenocortical cells derived from the males, and lowered corticosterone secretion by the cells obtained from the female glands only at a concentration of 10(-7) M. The lower concentration of melatonin increased ACTH (0.1 mU.ml-1)-stimulated corticosterone output by the cells of male and female rat adrenals. The pineal hormone was ineffective at a concentration of 10(-4) M, as well as in the presence of a higher dose of ACTH (1.0 mU.ml-1). These findings indicate a distinct sex-dependent effect of melatonin on in vitro cortisol and corticosterone production, and demonstrate that the modulatory effect of melatonin of the secretion of steroid hormones is more effective at lower concentrations.     

Effects of prostaglandins on adrenal steroidogenesis in the rat

To elucidate the role of prostaglandins in adrenal steroidogenesis, we studied aldosterone and corticosterone responses to 3 x 10(-8) M--3 x 10(-4) M of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), prostacyclin (PGI2), and arachidonic acid (AA) in collagenase dispersed rat adrenal capsular and decapsular cells. Whereas adrenocorticotrophic hormone (ACTH) and angiotensin II (AII) stimulated aldosterone production in capsular cells and ACTH stimulated corticosterone production in decapsular cells in a dose dependent fashion, aldosterone and corticosterone production were not stimulated significantly by PGE2, PGF2 alpha, PGI2, and AA. Although preincubation of dispersed adrenal cells with indomethacin (3 x 10(-5) M) markedly inhibited PGE2 synthesis, ACTH- and AII-stimulated aldosterone production and ACTH-stimulated corticosterone production were not attenuated despite prostaglandin blockade. These results indicate that prostaglandins are unlikely to play an important role in adrenal steroidogenesis.     

Hypertension, hypokalemia and hypoaldosteronism with suppressed renin: a clinical study of a patient with Liddle's syndrome

A 24-yr-old woman with hypertension, hypokalemic alkalosis, low plasma renin and hypoaldosteronism was studied. Plasma aldosterone, renin and potassium returned to normal and blood pressure fell after sodium restriction or the administration of triamterene. Thiazide therapy also normalized her blood pressure while dexamethasone, spironolactone and furosemide did not improve her symptoms. Plasma aldosterone levels were low and responded poorly to a short term ACTH injection, but responded well to the maximal adrenal stimulation by ACTH-Z. Plasma levels of cortisol, corticosterone and deoxycorticosterone were within the normal range. Adrenal scintigram with 131I-adosterol and abdominal computed axial tomography did not reveal the presence of a sizeable adrenal tumor. In addition, the urinary kallikrein excretion was low after sodium restriction and showed no response to saline infusion. These findings suggest that the excessive secretion of unusual mineralocorticoids may not exist in this case. From these observations and the results of the therapeutic responses to the diuretic agents, we conclude that the primary cause of the disorder of this patient seems to be a renal defect in the distal tubule in handling sodium and potassium which is similar to that in Liddle's syndrome.     

Further study of aldosterone secretion-inhibitory factor and brain natriuretic peptide on cortisol production of guinea pig zona fasciculata cells

The suppressive effect of aldosterone secretion-inhibitory factor (ASIF) and brain natriuretic peptide (BNP-32) on the basal and ACTH-stimulated cortisol production in a primary culture enriched with guinea pig Zona Fasciculata (ZF) cells was further studied. The binding of 125I-labeled ACTH(1-24) and ASIF to ZF cells was found to be displaced by ACTH(1-24), [Phe2, Nle4 and Ala24]-ACTH(1-24), ASIF, and BNP in a concentration-dependent manner. The binding of 125I-labeled [Phe2, Nle4 and Ala24]-ACTH(1-24) to two transformed clones of mammalian cells expressing the guinea pig ACTH receptor was also competitively inhibited by ASIF and BNP. ASIF and BNP significantly suppressed ACTH-stimulated cAMP production in ZF cells. The 10- and 30-min cellular changes in cAMP induced by ASIF and BNP did not correlate in the rank order with the ultimate magnitude of cortisol suppression observed in ZF cells after a 24-hour treatment with these peptides. Nevertheless, the results did conform to the signaling mechanism of their action. Overall, the findings clearly demonstrated that ASIF and BNP suppressed the adrenocortical function and inhibited ACTH for their antagonistic action against ACTH primarily at the ACTH receptor site. These results support the notion that a physiological role of adrenal medulla in regulating the adrenocortical function may be mediated by the neuropeptides through a paracrine pathway.     

Plasma cortisol and corticosterone concentrations in the golden hamster, (Mesocricetus auratus)

Because some recent studies of hamster adrenocortical function have depended on older studies that may have been inadequate or misinterpreted, the present study re-examined plasma corticosterone and cortisol concentrations in hamsters under several conditions to determine which plasma glucocorticoid predominated in this animal. Sensitive radioimmunoassays were used to measure separately the two glucocorticoids in the basal condition, after adrenocorticotropin (ACTH) treatment, after acute stress, and after chronic stress. In the basal condition, corticosterone concentrations were 3-4 times higher than those of cortisol. After stimulation, this difference disappeared, but rarely were any hamster's cortisol levels higher than their corticosterone levels. Both ACTH and acute stress elevated plasma corticosterone and cortisol concentrations, but only plasma cortisol concentrations were elevated following chronic stress. The dissociation between cortisol and corticosterone concentrations after chronic stress suggests that the two glucocorticoid hormones in the hamster may be regulated independently. The data also indicate that both corticosterone and cortisol should be measured when assessing adrenocortical function in the hamster.     

The effects of ageing on the morphology and function of the zonae fasciculata and reticularis of the rat adrenal cortex

Summary The morphological counterpart of the well-known age-dependent marked impairment of glucocorticoid secretion of rat adrenals was investigated by use of morphometric techniques. For this purpose 4-, 8-, 16- and 24-month-old rats were studied. Despite the notable lowering of both basal and ACTH-stimulated production of corticosterone by collagenase-dispersed inner adrenocortical cells, ACTH and corticosterone plasma concentrations displayed significant increases with ageing. Zona fasciculata (ZF) and zona reticularis (ZR) showed a notable hypertrophy in aged rats, which was due to rises in both the average volume and number of their parenchymal cells. The hypertrophy of ZF and ZR cells was in turn associated with increase in the volume of the mitochondrial compartment and proliferation of smooth endoplasmic reticulum, i.e., the two organelles involved in steroid-hormone synthesis. All these morphologic changes, conceivably due to the chronic exposure to high levels of circulating ACTH, are interpreted as a response enabling ZF and ZR to compensate for their age-dependent lowering in glucocorticoid secretion. Stereology also demonstrated that ZF and ZR cells underwent a striking age-related lipid-droplet repletion. Lipid droplets are the intracellular stores of cholesterol esters, the obligate precursors of steroid hormones in rats. This finding is in keeping with the contention that the mechanism underlying the age-dependent decline in rat-adrenal glucocorticoid secretion mainly involves impairments of the utilization of intracellular cholesterol previous to its intramitochondrial transformation to pregnenolone.