Doses Of ACTH Research Articles

163 ADRENAL RESPONSE DURING THE GRAFT-VERSUS-HOST (GVH) IN AN AVIAN MODEL

The GVH is a frequent complication of bone marrow transplantation (BMT) leading to a multi organ immune-mediated pathology. Its endocrine effects are difficlt to analyze in human pathology as BMT requires multiple regimen preparation frequently including radiotherapy. An avian model has been developped to more precisely investigate the endocrine complications of GVH. GVH was elicited on 9-day old chicken embryos by adult histo compatible spleen graft on the chorio allantoic membrane. The intensity of GVH was evaluated by the alteration of the embryo spleen. Adrenals from control and allografted animals were perifused (Endotronics, USA) during 2 hours and fractions collected every 10 minutes. In the controls, corticosterone production was constant during the perifusion period. Maximal corticosterone response occurs within 10-20 minutes after the injection of 1-24 ACTH. The optimal ACTH dose was 0.5 ug/ml. The adrenals of GVH animals shown basal secretion (6.0 ± 2.2 ng/ml/100 mg/10 mn) similar to the control. The maximal response to ACTH was constantly delayed (peak at the 20-30 minutes fraction) and significantly reduced compared to the control (400 % vs 900 % of the basal values). The present data favor adrenal resistance to ACTH. Such a resistance has been previously found in the thyroid on the same model. The exact mechanisms of this is presently under closer investigation.

Role of calcium ion in ACTH-induced steroidogenesis in humans

In order to examine the role of calcium ion in ACTH-induced steroidogenesis in humans, we carried out infusion of a pharmacological dose of ACTH (4.2 μg/kg) and a physiological dose of ACTH (0.0084 μg/kg) for 120 min, and infusion of dibutyryl cyclic AMP (DBcAMP) [0.33 mg/kg/min] for 20 min, in 22 normal subjects with or without verapamil treatment (360 mg/day, orally) for 5 days. The subjects were pretreated with 1.0 mg of dexamethasone and 5.0 mg of enalapril daily for 2 days before each infusion test to inhibit endogenous ACTH and angiotensin II. Following infusion of 0.0084 μg/kg of ACTH, plasma levels of corticosterone ( P < 0.02) and Cortisol ( P < 0.01) were significantly increased; with chronic verapamil treatment plasma levels of corticosterone ( P < 0.05) and cortisol ( P < 0.02) were significantly lower than those without verapamil. On the other hand, 4.2 μg/kg of ACTH for 120 min significantly increased the plasma levels of several steroid hormones, although there were no differences between the infusion with and without verapamil. Infusion of DBcAMP for 20 min significantly increased plasma levels of corticosterone ( P < 0.02) and cortisol ( P < 0.01), but verapamil did not affect the steroidogenic response to the DBcAMP infusion. The present results suggest that steroidogenesis induced by a physiological dose of ACTH diners from that after a pharmacological dose of ACTH or DBcAMP, and is mediated mainly by calcium ion as an intracellular messenger in man.

Suppression of LH response to gonadotrophin-releasing hormone or oestradiol by ACTH(1-24) treatment in anoestrous ewes.

Stress is known to result in lowered female reproductive efficiency. The objective of this study was to examine how increased pituitary-adrenal activity may influence gonadotrophin release in anoestrous ewes. Various doses (0.06-1.0 mg) of a synthetic adrenocorticotrophic hormone (ACTH(1-24)) preparation were injected into ewes 30 min or 3 h before an i.v. injection of 500 ng gonadotrophin-releasing hormone (GnRH). The LH response to GnRH given 30 min after ACTH(1-24) was similar to that after GnRH alone, whereas the response 3 h after ACTH(1-24) was significantly lower, irrespective of the dose of ACTH(1-24). At 30 min and 3 h after ACTH(1-24) the concentrations of cortisol exceeded 50 nmol/l compared with baseline values of less than 10 nmol/l. The effect of ACTH(1-24) on oestradiol-induced LH release was also examined. Those ewes receiving 0.8 mg ACTH(1-24) depot and 50 micrograms oestradiol benzoate simultaneously had a preovulatory-type increase in LH 14-20 h later, similar to when oestradiol benzoate was given alone. None of the ewes receiving an additional 0.8 mg ACTH(1-24) depot 10 h after oestradiol benzoate had increases in LH concentration. The cortisol concentrations in all ewes receiving either one or two injections of ACTH(1-24) were greater than 35 nmol/l at 10 h after the oestradiol injection. However, concentrations of progesterone increased from 0.9 +/- 0.3 (S.E.M.) nmol/l at the time of the second ACTH(1-24) injection to 2.1 +/- 0.3 nmol/l after 2 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-training and pretest effects of adrenocorticotropin on retention: the influence of the hour of the day, the training-test interval, and pretest naloxone administration

Rats received an ip injection of 0.2 microgram/kg of ACTH-(1-39) 1 min after step-down inhibitory avoidance training and/or 5 min prior to retention testing. Experiments were carried out either in the morning or in the afternoon using either a 3- or a 24-h training-test interval. Post-training ACTH induced memory facilitation in the morning and amnesia in the afternoon at both training-test intervals. Pretest ACTH reversed the afternoon amnesic effect, also at both training-test intervals. In addition, pretest ACTH induced a naloxone-reversible memory enhancement, both on its own and in animals treated with a facilitatory post-training dose of ACTH in the morning; this effect was seen only at the 24-h training-test interval. Naloxone had no effect of its own and did not influence the reversal of ACTH-induced amnesia caused by pretest ACTH in the afternoon. The results point to the variety of memory modulatory influences of ACTH, and to some of the factors involved in the elicitation of one or other effect, namely, the presumable basal rate of secretion of endogenous ACTH, and the previous pharmacological history of the animal.

Evidence that prolonged α-MSH infusion enhances the steroidogenic capacity of rat adrenal zona glomerulosa in vivo

Prolonged infusion with 120 μg/kg/day α-MSH significantly increased basal plasma level of aldosterone in the rat, as well as raised the acute aldosterone response to a bolus administration of a high dose of ACTH or angiotensin II. These findings suggest that chronic α-MSH treatment stimulates the steroidogenic capacity of rat zona glomerulosa.

Naloxone-like influence of TRH and ACTH-(4–7) on hypothalamic blood flow autoregulation in the rat

The influence of intracerebroventricularly (ICV) administered thyrotropin-releasing hormone pGlu-His-Pro-NH 2 (TRH), pGlu-His-Phe-NH 2 (TRH analog, (TRHa)), Met-Glu-His-Phe(ACTH-(4–7)) and His-Phe-Arg-Trp-Gly (ACTH-(6–10)) on autoregulation of cerebral blood flow was studied in anesthetized, ventilated rats. Autoregulatory capacity of the cerebrovascular bed was tested by hypothalamic blood flow (HBF) and total cerebral blood volume (CBV) determinations during consecutive stepwise lowering of the systemic mean arterial pressure to 80, 60 and 40 mmHg, by hemorrhage. None of the peptides caused a change in resting HBF or CBV upon ICV administration (5 μg/kg). However, the same dose of TRH, TRHa and ACTH-(4–7) resulted in impairment of autoregulation. ACTH-(6–10) was not effective. Thus, the disturbed autoregulation may be due to the presence of the dipeptide Glu-His which is common to TRH, TRHa and ACTH-(4–7).

The role of cyclic nucleotides in atrial natriuretic peptide-mediated inhibition of aldosterone secretion.

Using freshly isolated bovine adrenal glomerulosa cells we examined the inhibitory effect of atrial natriuretic peptide (ANP) on aldosterone secretion stimulated by agonists that use either the Ca2+-phosphoinositide or cAMP messenger system. In a continuous perifusion system, angiotensin II (AII) induces a prompt initial rise in aldosterone secretion, followed by a sustained secretory response. Both phases of secretion are rapidly and independently inhibited by ANP. The role of two cyclic nucleotides, cGMP and cAMP, as mediators of this ANP-induced inhibition was examined. The effect of 8-bromo-cGMP (1-100 microM) or (Bu)2cGMP (1-50 microM) on the AII-stimulated rate of secretion was studied in a perifusion system. Either analog, whether added early or late, maximally inhibited by 20-30% only the late or sustained phase of aldosterone secretion. The effect of ANP on cellular cAMP content was examined in a static incubation system. Although ANP caused a reduction in the cAMP content of cells stimulated with either AII or ACTH, it had little or no effect on the cAMP levels in cells stimulated with carbachol. In AII- and ACTH-stimulated cells, the relationship between reduced cAMP content and reduced secretion was explored. In the AII-stimulated cell inhibited by ANP, simple restoration of cAMP content with forskolin did not restore the secretory rate. Pertussis toxin treatment blocked the inhibitory effect of ANP on cAMP content, but did not block its inhibition of secretion. In the ACTH-stimulated cell, reversal of the ANP-induced reduction of cAMP with forskolin, partially restored the stimulated rate of secretion, although restoration of cAMP with a 10-fold higher dose of ACTH did not restore the stimulated rate of secretion in the presence of ANP. These results imply that both the ANP-induced rise in cGMP and the ANP-induced decrease in cellular cAMP content may contribute to the inhibition of steroidogenesis. However, these inhibitory messages do not induce either the magnitude or the temporal pattern of inhibition induced by ANP. Thus, in the adrenal multiple messenger systems may underlie the action of ANP.

Stress-induced hypokinesia is facilitated by ACTH-(7–10)

Subcutaneous treatment with the neuropeptide ACTH-(4–10) induced hypokinesia in rats subjected to a mild stress induced by placing the animals on a non-functional “hot” plate (21°C) for 30 sec, but not in control animals not exposed to this stress-inducing environment. The lowest effective dose of ACTH-(4–10) was 5 μg/kg, administered 50 min before testing. The combination of peptide treatment and the mild stress-inducing procedure mimicked the effect of a short intense stress induced by placing the rats on a hot plate (57°C) for 30 sec, suggesting that this stress-induced hypokinesia is mediated by ACTH neuropeptides. Structure-activity relationship studies revealed that the active core for the ACTH-(4–10)-induced hypokinesia is located in the C-terminal tetrapeptide Phe-Arg-Try-Gly (ACTH-(7–10)). Pretreatment with the opioid antagonist naltrexone did not influence the effect of ACTH-(4–10) indicating that activation of opioid systems is not implicated in this behavioral effect of the peptide.

Modulation of the immune response by proopiomelanocortin derived peptides: II. Influence of adrenocorticotropic hormone on the rise in intracellular free calcium concentration after T cell activation

In this paper the effect of ACTH 1-24 is described on one of the “early events” occurring during T cell activation: the rise in the concentration of cytosolic free calcium. The increase in cytosolic free calcium induced by concanavalin A or by a monoclonal antibody with specificity for the T cell receptor-T3 complex could be modulated by physiological concentrations of ACTH 1-24. The modulation of the response appeared to be dose dependent. The effect of ACTH 1-24 was maximal at 10 −10 M. No effect of ACTH 1-24 was observed on the basal level of cytosolic free calcium. These results indicate that physiological doses of ACTH can interfere with the responsiveness of T cells to mitogenic and antigenic stimuli.

Some characteristics of TRH-induced grooming behavior in rats

Intracerebroventricular administration of TRH induces excessive grooming behavior that is characterized by an important contribution of the elements scratching and paw licking. As compared with other grooming inducing peptides, the pattern of TRH-induced grooming resembles that induced by β-endorphin rather than those elicited by ACTH or bombesin. TRH-induced excessive grooming is suppressed by pretreatment with haloperidol, naloxone or neurotensin. Haloperidol suppresses TRH-induced grooming in a general way, whereas the suppressive effect of the other drugs is mainly due to a selective reduction of TRH-induced excessive scratching. Combined treatments of rats with TRH and a submaximal dose of ACTH, bombesin or β-endorphin do not result in higher grooming scores than with single peptide treatment. Excessive grooming elicited by water immersion is not affected by TRH. It is concluded that TRH is undoubtedly an excessive grooming inducing peptide. In situations where excessive grooming is elicited by other peptides or by water immersion, TRH does not further activate the operating systems involved in the existing excessive grooming.

The Role of Adrenocorticotropin in the Cortisol and Aldosterone Responses to Angiotensin II in Conscious Dogs*

The role of ACTH in the cortisol and aldosterone responses to iv angiotensin II (AII) infusion, (5, 10, and 20 ng kg-1 min-1) in dogs was evaluated by examining the effect of AII infusion in conscious dogs pretreated with dexamethasone to suppress endogenous ACTH secretion. AII infusion in untreated dogs produced dose-related increases in plasma cortisol and aldosterone concentrations. The plasma ACTH concentration also increased. Dexamethasone treatment lowered the basal cortisol concentration from 1.7 +/- 0.1 to 0.7 +/- 0.1 micrograms/dl (P less than 0.05) and the ACTH concentration from 52 +/- 3 to 41 +/- 4 pg/ml (P less than 0.05), and abolished the cortisol response to all doses of AII, indicating that ACTH was necessary for the response. On the other hand, the basal aldosterone concentration was not significantly affected by dexamethasone, although the aldosterone response to the highest dose of AII was reduced. Additional experiments were performed to determine if the cortisol and aldosterone responses to AII (20 ng kg-1 min-1) in dexamethasone-treated dogs are restored if the ACTH concentration is maintained near control levels by iv infusion of synthetic alpha ACTH-(1-24) (0.3 ng kg-1 min-1). AII still failed to increase the plasma cortisol concentration in this group of dogs; however, the aldosterone response was fully restored. To evaluate the effect of elevated ACTH levels on the steroidogenic effects of AII, dogs were treated with dexamethasone and a higher dose of ACTH (0.4 ng kg-1 min-1). This dose of ACTH increased the plasma cortisol concentration from 1.7 +/- 0.1 to 3.5 +/- 0.8 micrograms/dl (P less than 0.05), but did not significantly affect the plasma aldosterone concentration. In the presence of constant elevated levels of ACTH, AII (10 and 20 ng kg-1 min-1) increased the plasma cortisol concentration in dexamethasone-treated dogs, although the response to the 10 ng kg-1 min-1 dose was smaller than the response in untreated dogs. Infusion of AII at 5 ng kg-1 min-1 did not increase the plasma cortisol concentration. In contrast, the increased plasma aldosterone produced by AII infusion in dexamethasone-treated dogs was not altered in the presence of elevated ACTH levels. Finally, AII infusion did not alter the clearance of cortisol. Collectively, these results demonstrate that an increase in plasma ACTH is necessary for the cortisol response to AII infusion.(ABSTRACT TRUNCATED AT 400 WORDS)

EFFECT OF 3 DAY INFUSION OF ACTH OR CRF ON THE PITUITARY‐ADRENAL AXIS

1. The effects of 72 h subcutaneous infusion of graded doses of rat CRF and ACTH(1-24) were studied in rats of initial weight 150-170 g. Rat CRF was infused at 30, 100 or 300 ng/h, and ACTH(1-24) at 125, 250 or 500 ng/h. 2. There was a progressive though modest increase in adrenal weight for all CRF doses, and an associated reduction of thymus weight. Circulating ir-ACTH, ir-beta-endorphin and corticosterone levels, and adrenal DNA content, were not increased after 3 days. Adrenal RNA and protein content were increased at the highest CRF dose used. 3. ACTH infusion caused a progressive increase in adrenal weight and thymic involution which was marked at the higher doses; circulating corticosterone levels were not significantly altered by the lowest dose but were significantly raised by the higher doses. As expected, plasma ir-beta-endorphin was suppressed to low levels with all doses. Adrenal DNA did not alter but there were progressive increases in adrenal protein and RNA. 4. There was a marked difference in gain between the two infusion regimens in terms of all parameters measured, suggesting that potent mechanisms exist to temper the pituitary-adrenal response to markedly different levels of peripheral CRF input. The damped effect of CRF infusion compared with that of ACTH may represent desensitization of CRF receptors at the pituitary; alternatively, it may reflect binding and substantial inactivation of CRF in peripheral blood.

Infantile Spasms and ACTH Dosage

Results of corticotropin treatment of 33 patients with infantile spasms are reported from the Instituto Clinica Pediatrica, Universita di Siena, Italy.

Factors controlling adrenal weight and corticosterone secretion in male rats as revealed by median eminence lesions and pharmacological alteration of prolactin secretion

To determine whether or not prolactin, as well as ACTH, was involved in the control of adrenal weight and steroid release, lesions in the median eminence which had previoulsy resulted in impaired steroid release and atrophy of the adrenal were placed in animals in which the plasma prolactin was allowed to rise as a result of the lesions or prevented from rising by the administration of the dopamine agonist, CB-154. As previously reported, as the severity of diabetes insipidus (DI) increased as a result of interruption of the supraoptico-hypophyseal tract, adrenal weight declined reaching a nadir at water intakes of approximately 100–150 ml/day. This was followed by a reversal of this trend and an increase in adrenal weight as water intakes increased further. These effects were not modified by CB-154 which was effective to lower the elevated prolactin levels in the animals. In general, adrenal weight correlated with levels of plasma corticosterone and progesterone. The ability of the animals to undergo compensatory adrenal hypertrophy was also impaired by median eminence lesions in the presence or absence of CB-154. Exceptional animals were encountered in which adrenal weight was high and yet plasma corticosterone was low. Treatment of hypophysectomized animals with long-acting ACTH plus maintenance doses of triiodothyronine prevented the adrenal atrophy characteristic of the hypophysectomized animal, thus confirming that ACTH is the most important hormone in the control of adrenal weight. Some role for prolactin is suggested by the fact that elevation of prolactin via the drinking of sulpiride, a dopamine receptor blocker, was associated with a relatively small elevation of adrenal weight and plasma corticosterone. In the animals with lesions, blockade of adrenal function was always found in animals with complete lesions of the median eminence and was usually found if the lesion destroyed the anterior median eminence and extended caudally to the separation of the pituitary stalk. Lesions of the paraventricular nucleus did not block adrenal function, presumably because sufficient CRF neurons were located outside this structure to maintain adrenal function and/or because of the maintenance of considerable vasopressin secretion. Defective adrenal function was usually associated with DI indicative of interruption of the supraoptico-hypophyseal tract and deficient vasopressin secretion; however, several animals were found which had relatively high degrees of DI and yet adrenal function was relatively normal suggesting that CRF is more important than vasopressin in the control of ACTH secretion. Since some animals had relatively normal adrenal function and weight in the presence of severe damage to the median eminence it is possible that other pituitary factors, the release of which would be increased by such lesions, such as α-MSH, may play a role in maintenance of adrenal weight. The possible participation of neural factors also cannot be ruled out.

Adrenal cortical responses to vasoactive intestinal peptide in conscious hypophysectomized calves.

1. Right adrenal and various cardiovascular responses to an intra-aortic infusion of vasoactive intestinal polypeptide (VIP; 4 micrograms min-1 kg-1) have been investigated in the presence and absence of exogenous adrenocorticotrophin, (ACTH1-24; 5 ng min-1 kg-1, i.v.). The adrenal clamp technique was employed in conscious calves in which the pituitary stalk had been cauterized 3-4 days previously. 2. The i.v. infusion of ACTH1-24 increased mean plasma ACTH concentration by between 1000 and 1100 pg ml-1 and mean right cortisol output by about 700 ng min-1 kg-1. Under these conditions the intra-aortic infusion of VIP produced a further rise in mean adrenal cortisol output, together with a consequential rise in mean arterial plasma cortisol concentration, without affecting the concentration of ACTH in the arterial plasma significantly. In the absence of ACTH the same infusion of VIP had no detectable effect on adrenal cortisol output. 3. In each of the above respects this intra-aortic infusion of VIP closely mimicked the effect of stimulation of the peripheral end of the right splanchnic nerve in these animals, as it also did by causing a substantial fall in adrenal vascular resistance in the absence, but not in the presence, of ACTH. 4. It is concluded that release of this peptide from splanchnic nerve terminals in the adrenal gland most probably accounts, at least in part, for the powerful adrenocortical steroidogenic response to splanchnic nerve stimulation, that occurs in the presence of submaximal doses of ACTH.

An Improved in Vitro Bioassay for Follicle-Stimulating Hormone (FSH): Suitable for Measurement of FSH in Unextracted Human Serum*

FSH bioactivity was measured by means of FSH-dependent aromatase activity (conversion of androgen substrate to estradiol). Assay sensitivity was optimized by the use of immature (7-10 days old) rats as Sertoli cell donors, serum-free medium for incubation, phosphodiesterase inhibitor (methylisobutylxanthinine), serial dilution of FSH in medium containing 1% BSA, delayed addition of FSH for 72 h after cell plating, and 19-hydroxyandrostenedione (2.5 X 10(-6) M) as the aromatizable androgen substrate. The method consisted of subjecting the decapsulated immature rat testes to a 2-step collagenase dispersion, plating the cells in medium [Dulbecco's Modified Eagle's Medium-Ham's F-10 (1:1)] containing growth factors and methylisobutylxanthinine for 72 h, adding increasing doses of FSH to the standard curve or small volumes of serum to the test vials as well as 19-hydroxyandrostenedione for 24 h, and measuring estradiol by RIA in dilutions of the medium. Using NIAMDD human (h) FSH-2 as the bioassay standard, the useful range of the assay was 0.01-5.0 ng/ml. Specificity was determined by the addition of graded doses of hLH, hTSH, ACTH, hGH, hPRL, and hCG. The minor degree of FSH bioactivity observed in a few hormone preparations was accounted for by the degree of FSH contamination in them. Mean intra- and interassay coefficients of variation were 9% and 11%, and the index of precision was 0.049. This bioassay was used to determine the bioactive FSH content of pituitary extracts, tissue culture media, elutions from columns, and isoelectrically focused samples. More importantly, small quantities of human sera gave responses parallel to the standard curve in a minimum of two dilutions. The bio- to immunoreactive ratios, expressed as the mean +/- SEM (NIAMDD-hFSH-2), were 0.66 +/- 0.2 in boys (n = 6), 0.78 +/- 0.2 in pubertal girls (n = 6), 1.18 +/- 0.2 in men (n = 13), 1.24 +/- 0.1 in postmenopausal women (n = 30), 1.94 +/- 0.3 in the follicular phase (n = 19), 6.2 +/- 1.4 in the ovulatory phase (n = 19), and 1.6 +/- 0.4 in the luteal phase (n = 19) of the normal menstrual cycle. These results indicate that the bio- to immunoreactive hFSH ratio in the circulation, is dependent upon the hormonal milieu of the subject.

Adrenocortical function in acquired immunodeficiency syndrome.

Clinical features of adrenal steroid deficiency occur in patients with the acquired immunodeficiency syndrome (AIDS). To determine the frequency of aberrations in peripheral steroid levels in patients with AIDS and AIDS-related complex (ARC) we measured morning recumbent plasma cortisol, deoxycorticosterone, 18-hydroxydeoxycorticosterone (18-OHDOC), corticosterone, aldosterone, and 18-hydroxycorticosterone concentrations before and after administration of 0.25 mg ACTH (Cosyntropin) in 74 randomly selected hospitalized patients with AIDS and 19 patients with ARC. Basal (0800 h) cortisol levels in the AIDS patients were significantly higher (P less than 0.01) than those in normal subjects, while other ACTH-dependent steroids of the 17-deoxypathway, deoxycorticosterone, corticosterone, and 18-OHDOC, were normal. These latter steroids increased subnormally in response to ACTH in patients with either AIDS (P less than 0.001) or ARC (P less than 0.005), but in ARC patients plasma 18-OHDOC levels were significantly higher than in those with AIDS (P less than 0.001). Supraphysiological doses of ACTH were then administered for 3 consecutive days to 14 patients with AIDS and 9 with ARC, which confirmed and amplified the subnormal responses of these steroids in AIDS. The mean plasma cortisol response was reduced on the third day only in AIDS patients, whereas in the ARC patients the steroid responses were normal. Angiotensin III infusion and postural stimulation increased plasma aldosterone and 18-hydroxycorticosterone levels in AIDS and ARC patients. Defective stimulation of 18-OHDOC alone or in combination with defective stimulation of other 17-deoxysteroids can be a harbinger of subsequent impaired adrenal capacity in AIDS.

Uptake and Release of Adrenal Ascorbic Acid in the Guinea Pig after Injection of ACTH

The effect of a single injection of ACTH (3 KI/100 g body weight) on the distribution of ascorbic acid (AA) and radiolabeled AA in 20 tissues was studied in adult male guinea pigs consuming 500 mg AA/kg diet. Saline- or ACTH-injected animals were simultaneously injected with [1-14C]AA, and killed at 0.5, 1, 2, 4 and 6 h after injection. There was no significant difference between treatments in the weight of any tissue over the 6-h experimental period. As anticipated, the concentration of AA in the adrenals of animals injected with ACTH was 33% of that of animals injected with saline at 4 h. Unexpectedly, the concentration of radiolabeled AA in the adrenals at 0.5 h after ACTH injection was 172% of that after saline injection. The concentration of radiolabeled AA in the adrenal of the saline-injected animals increased slowly over time to reach a level similar to that of ACTH-injected animals by 6 h. There was no effect of ACTH on the level of AA or uptake in any of the other tissues examined. These results demonstrate that a single dose of ACTH markedly influences the retention of AA in the adrenal gland without similarly altering retention of AA in other tissues. Furthermore, ACTH treatment causes both accelerated uptake and release of AA into the adrenals.

Hypothalamo-pituitary-adrenal function in infantile spasms: effects of ACTH therapy.

The metyrapone test was used to study the hypothalamo-pituitary-adrenal function in ten children with infantile spasms, before and after ACTH treatment. The hypothalamo-pituitary-adrenal response was normal before ACTH treatment in almost all children. After ACTH, the responses of two children were suggestive of a diminished pituitary reserve; three were suggestive of decreased adrenal as well as decreased pituitary reserve, and one suggested either adrenal hyperplasia with normal pituitary reserve, or appropriate response to a developing medical stress. We suggest that, in children being treated with ACTH, the dosage of ACTH should be gradually tapered, AM cortisol levels should be monitored, and high-dose steroids should be included when treating medical stress.

Hormonal regulation of messenger ribonucleic acids for P450scc (cholesterol side-chain cleavage enzyme) and P450c17 (17 alpha-hydroxylase/17,20-lyase) in cultured human fetal adrenal cells.

ACTH has acute and long term effects on adrenal steroidogenesis by week 14 of fetal life. We used human fetal adrenal cells to investigate the long term effect of physiological doses of ACTH on mRNAs for P450scc (the cholesterol side-chain cleavage enzyme) and P450c17 (17 alpha-hydroxylase/17,20-lyase). Monolayer cultures of 18- to 24-week gestation fetal zone adrenal cells were maintained in the presence and absence of 10(-9) or 10(-8) M ACTH for up to 12 days. As assessed by RNA dot blots probed with cloned homologous human cDNAs, ACTH increased P450scc and P450c17 mRNAs 4- and 9-fold, respectively, over control values on day 7 of culture. ACTH-mediated stimulation was slightly less on day 12 of culture. The ACTH-mediated accumulation of those mRNAs were time dependent. When cells were exposed to a single 10(-8)-M dose of ACTH, the amount of P450scc and P450c17 mRNA was increased by 24 h, reaching a maximum at 48 h and diminishing by 72 h. When cells were maintained in 10(-8) M ACTH continuously, mRNA for both enzymes accumulated in a similar pattern, reaching a peak at 48 h but remaining at nearly maximal values thereafter, up to 96 h. Dibutyryl cAMP (10(-3) M) mimicked these stimulatory actions of ACTH, although its effect was greater at 24 h and more stable up to 96 h. Angiotensin II (1-100 ng/mL) and hCG (1-100 ng/mL) had no effect on accumulation of P450scc and P450c17 mRNAs. The production of both dehydroepiandrosterone sulfate and cortisol also was stimulated by ACTH, suggesting that the increased mRNAs were translated into active enzymes. These results indicate that ACTH induces human fetal adrenal cells to accumulate mRNAs for both P450scc and P450c17; this effect of ACTH is probably mediated by cAMP. Chronic 96-h stimulation of human fetal adrenal cells did not diminish their responsiveness to ACTH. Together with our earlier studies of the human fetal adrenal, these data indicate that fetal adrenal tissue does not exhibit the desensitization to trophic hormone stimulation characteristic of adult tissue.