Ectopic adrenocorticotropin syndrome caused by lung cancer that responded to corticotropin-releasing hormone

ACTH responses to corticotropin-releasing hormone (CRH) were studied in three patients with the ectopic ACTH syndrome caused by lung cancer. Plasma ACTH responded to synthetic CRH in two of three patients. Tumor tissues obtained from these two patients contained CRH and ACTH. In one patient, tumor ACTH secretion was stimulated by CRH in vitro. Tumor CRH was immunologically, chromatographically, and biologically similar to hypothalamic CRH. In addition, multiple forms of immunoreactive beta-endorphin were present in plasma and the tumor extracts. From these results, we conclude that some patients with the ectopic ACTH syndrome have tumors that produce both ACTH and CRH and that CRH can stimulate ACTH secretion by such tumors. Other patients with the ectopic ACTH syndrome do not have ACTH responses to CRH. Therefore, procedures other than CRH testing are needed to differentiate patients with Cushing's syndrome due to ectopic ACTH/CRH production from those with Cushing's disease, since the latter also usually have ACTH responses to CRH.     

Effects of immune neutralization of corticotropin-releasing hormone, adrenocorticotropin, and beta-endorphin in the surgically stressed rat

Specific in vivo neutralization was used in an attempt to explore the roles of corticotropin-releasing hormone (CRH), ACTH, and beta-endorphin during surgical stress in Sprague-Dawley rats. Rats were randomly assigned to groups (n = 20-30/group) that received iv injections of rabbit antirat/human CRH (anti-r/hCRH), antihuman ACTH (anti-hACTH), antihuman beta-endorphin (anti-h beta-endorphin), or normal rabbit serum. Three hours later all animals were subjected to a uniform stress consisting of ether anesthesia, surgical laparotomy, and phlebotomy of 7 ml via the inferior vena cava. Survival rates were recorded, and RIAs were performed for ACTH, beta-endorphin, and corticosterone. Rats treated with anti-h beta-endorphin had a survival rate of 64%, which was significantly higher than that of the control group (33%; P less than 0.025, by analysis of variance). Anti-r/hCRH or anti-hACTH treatment was not associated with a change in survival rate. Plasma immunoreactive beta-endorphin levels were markedly decreased in the group treated with anti-h beta-endorphin (P less than 0.0001). Anti-r/hCRH had no effect on plasma immunoreactive ACTH or beta-endorphin. Plasma immunoreactive ACTH and corticosterone levels were decreased in the group treated with anti-hACTH (P less than 0.0001 and P less than 0.01, respectively). We conclude that 1) beta-endorphin immune neutralization is associated with a survival advantage during severe surgical stress, suggesting that circulating beta-endorphin might have deleterious effects during stress; 2) In severe stress, acute immune neutralization of CRH is not sufficient to inhibit ACTH, beta-endorphin, and corticosterone secretion, suggesting significant involvement of other secretagogues of the pituitary-adrenal axis; and 3) moderate decreases in corticosterone cannot affect survival, presumably because glucocorticoids play only a permissive role in maintaining cardiovascular stability during surgical stress.     

In vivo corticotropin-releasing factor-induced secretion of adrenocorticotropin, beta-endorphin, and corticosterone

A 41-residue peptide purified as a corticotropin-releasing factor/beta-endorphin-releasing factor (CRF) in vitro was tested for its ability to stimulate the secretion of ACTH, beta-endorphin, and corticosterone in three animal groups: 1) unanesthesized rats bearing indwelling venous cannulae, 2) rats pretreated with chloropromazine plus morphine sulfate plus pentobarbital (CPZ-MS-Nb, and 3) rats with hypothalamic deafferentiations in the frontal and lateral retrochiasmatic areas. In all three bioassays iv administration of 0.1-10 micrograms CRF elicited a dose-related increase in plasma ACTH and beta-endorphin values over a 5- to 15-min period. Corticosterone secretion was also elevated but responded maximally with all doses of CRF tested. Pretreatment of CPZ-MS-Nb animals with 20 micrograms dexamethasone 4 h before assay abolished the CRF-induced hormone secretion. These data suggest that CRF may play a physiological role in the regulation of the hypothalamic-pituitary-adrenal axis.     

Effects of immunoneutralization of corticotropin-releasing hormone on ultradian rhythms of plasma adrenocorticotropin

ACTH, like other anterior pituitary peptide hormones, is secreted episodically and demonstrates both circadian and ultradian rhythms. CRH is the major regulator of ACTH release from the pituitary corticotroph. To determine the dependence of ACTH ultradian rhythms on CRH, passive immunoneutralization was used to block the activity of endogenous CRH in rats with indwelling venous catheters. Blood was sampled at 2- and 15-min intervals while blood volume was replaced. Plasma ACTH was measured by RIA. Time-series analysis of plasma ACTH concentrations was performed with PULSAR and Cluster Analysis. The 2 min data demonstrated secretory bursts approximately every 20 min. CRH immunoneutralization had no effect on the frequency of these pulses, but significantly reduced their amplitude. This was the case for raw data as well as data in which lower frequency variation had been filtered out. The 15 min data demonstrated pulsatile secretion, with a secretory episode approximately every 100 min. This lower frequency rhythm was also observed when high frequency components were filtered out of the 2 min data series. Analysis of the 15 min and the filtered 2 min time series showed this rhythm to be almost totally ablated by CRH immunoneutralization. These results suggest that CRH is responsible for amplitude modulation of an underlying CRH-independent rhythm and that through intermittent amplitude modulation of this rhythm a lower frequency rhythm is generated. Comparison between treatment groups of pulses identified by PULSAR or Cluster Analysis yielded similar results, but the programs were discordant with each other. This is the first in vivo evidence of pulsatile ACTH secretion independent of CRH, the first report demonstrating that different ultradian rhythms of ACTH may be regulated by different mechanisms, and the first comparison of PULSAR and Cluster Analysis on plasma ACTH time series.     

Circadian patterns of plasma immunoreactive corticotropin, beta-endorphin, corticosterone and prolactin after immunoneutralization of corticotropin-releasing hormone.

To study the role of corticotropin-releasing hormone (CRH) in the circadian rhythm of circulating corticotropin (ACTH), beta-endorphin (beta-END), corticosterone, and prolactin (PRL), we measured the effects of CRH immunoneutralization over a 24-hour period in chronically cannulated, conscious, freely moving, male Sprague-Dawley rats, maintained at a constant light-dark cycle. Blood samples were collected in the morning (08.00 h), at noon (12.00 h), and in the evening (18.00 h) on the day of treatment, and in the morning (08.00 h) of the next day. Hyperimmune rabbit serum raised against rat CRH (1.0 ml/rat, i.v.) or normal rabbit serum (NRS, 1.0 ml/rat, i.v.) was administered at 08.00 h, immediately after the first blood sample had been collected. CRH immunoneutralization caused no significant decreases in circulating immunoreactive ACTH, beta-END and corticosterone plasma levels at noon, but abolished the evening rises of these hormones. PRL levels were not significantly different between the groups at any time point measured. To compare the effects of CRH immunoneutralization to those of glucocorticoid negative feedback, we measured the effects of dexamethasone (0.5 mg/kg, i.v. at 08.00 h) on the above parameters. ACTH and beta-END concentrations were significantly decreased, and corticosterone and PRL levels were markedly suppressed after glucocorticoid administration both at 12.00 and 18.00 h. However, 24 h after the administration of dexamethasone, PRL concentrations were elevated despite persistently low corticosterone levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Responses of plasma adrenocorticotropin, cortisol, and dehydroepiandrosterone to ovine corticotropin-releasing hormone in healthy aging men

To assess the effects of age on both the pituitary ACTH response to corticotropin-releasing hormone (CRH) and the secretory responses of cortisol (F) and dehydroepiandrosterone (DHEA) to endogenous rises in ACTH, we measured evening basal and ovine CRH (oCRH; 1 mu/kg)-stimulated plasma concentrations of ACTH,F, and DHEA in 49 healthy men, aged 21-86 yr. By analysis of variance, we found no change with age in either the basal concentration of ACTH or the magnitude of the peak ACTH response to oCRH. Older men had higher basal F levels (P less than 0.05), while basal plasma levels of CBG and ratios of F to CBG did not vary significantly with age (P greater than 0.1). We also found no significant increase with age in the magnitude of the peak F response to oCRH (P greater than 0.2), although peak F responses occurred significantly earlier (P less than 0.03) in the older men. Basal plasma levels of DHEA decreased significantly with age (P less than 0.001), as did the magnitude of peak DHEA responses to endogenous ACTH rises (P less than 0.01). There was no alteration in the timing of the peak DHEA response with age (P greater than 0.7). We conclude that while ACTH and F responses to evening injections of oCRH are well maintained in healthy aging men, that of DHEA is discordantly decreased. The present findings are compatible with the hypotheses that there is a diminished sensitivity of ACTH secretion to negative feedback regulation by glucocorticoids in older men, and there is an ACTH-independent age-related diminution in adrenal androgen secretion.     

Influence of human corticotropin-releasing hormone and adrenocorticotropin upon spontaneous growth hormone secretion.

Hormones of the hypothalamo-pituitary-adrenocortical (HPA-) axis are considered to be of physiological and clinical relevance in regulating spontaneous growth hormone (GH) secretion. To further investigate interdependencies between both systems, we studied the effects of adrenocorticotropin [ACTH(1-24)] and human corticotropin-releasing hormone (h-CRH) upon spontaneous GH secretion in 10 male volunteers. Administration of 1 microgram ACTH (1-24), 10 micrograms h-CRH or saline (control: CTL) every hour from 9.00 to 6.00 p.m. resulted in significant differences of cortisol secretion during the entire observation period (8.00 a.m.-3.00 a.m.) between the three groups (p less than 0.001, Friedman two-way ANOVA). Mean area under the time course curve (AUC) values (+/- SEM) for cortisol expressed as ng x 1,000 x min/ml showed also significant differences between the three treatments from 8.00 a.m. to 3.00 a.m.: CTL 64.0 +/- 6.4, ACTH(1-24) 178.5 +/- 9.4 (p less than 0.01, Wilcoxon test), h-CRH 88.5 +/- 5.6 (p less than 0.01). The main portion of cortisol was released during daytime from 8.00 a.m. to 11.00 p.m., where the most significant differences in the AUC values emerged: CTL 59.6 +/- 5.8, ACTH(1-24) 171.5 +/- 8.8 (p less than 0.01, Wilcoxon test), h-CRH 80.2 +/- 5.1 (p less than 0.01). With regard to GH secretion, significant differences became obvious between the three treatments during daytime from 8.00 a.m. to 11.00 p.m. and the sleep-related period from 11.00 p.m. to 3.00 a.m. (p less than 0.01 and p less than 0.02, Friedman two-way ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ovine corticotropin-releasing hormone administered during insulin-induced hypoglycemia on plasma adrenocorticotropin and cortisol

The factors that mediate the hypothalamic-pituitary response to hypoglycemia in man are unknown. To investigate the role of CRH in the plasma ACTH response to hypoglycemia, two different doses of ovine CRH (oCRH) were given to normal men during insulin-induced hypoglycemia. We hypothesized that if the endogenous CRH response to hypoglycemia were less than maximally stimulating, administration of oCRH during hypoglycemia would result in a greater peak plasma immunoreactive (IR) ACTH response. Six normal men were given 1) 0.15 U/kg regular insulin, iv; 2) insulin plus 1 microgram/kg oCRH, iv, 5 min after serum glucose fell to 40 mg/dL or less; and 3) oCRH alone. The degree and duration of hypoglycemia were the same when insulin was given alone or with oCRH. Plasma IR-ACTH after insulin alone and insulin plus oCRH rose at the same rate to similar peaks of 226 +/- 37 (mean +/- SEM) and 213 +/- 53 pg/mL, respectively, both of which were greater (P less than 0.05) than the peak plasma IR-ACTH after oCRH alone (61 +/- 19 pg/mL). The peak plasma IR-cortisol levels after insulin alone (24 +/- 4 micrograms/dL), insulin plus oCRH (27 +/- 3 micrograms/dL), and oCRH alone (18 +/- 2 micrograms/dL) were not significantly different. In a second study, six normal men were given 0.15 U/kg regular insulin, iv; insulin plus 10 micrograms/kg oCRH, iv; and 10 micrograms/kg oCRH alone. Administration of oCRH 5 min after serum glucose fell to 40 mg/dL or less did not affect the degree or duration of hypoglycemia. Plasma IR-ACTH after insulin alone and insulin plus oCRH rose at the same rate to similar peaks of 258 +/- 14 and 290 +/- 33 pg/mL, respectively, both of which were greater (P less than 0.01) than the peak (54 +/- 6 pg/mL) after oCRH alone. After insulin alone, plasma IR-ACTH declined to baseline by 3 h. However, after insulin plus oCRH, plasma IR-ACTH fell gradually until 2 h, rose to a second peak at 2.5-3 h, and remained greater (P less than 0.01) than after insulin or oCRH alone for the 4-h duration of the study. The mean peak plasma IR-cortisol level after insulin plus oCRH (33 +/- 4 micrograms/dL) was similar to that after insulin alone (28 +/- 3 micrograms/dL), but was greater (P less than 0.05) than that after oCRH alone (18 +/- 2 micrograms/dL).(ABSTRACT TRUNCATED AT 400 WORDS)     

Human plasma proopiomelanocortin N-terminal peptide and adrenocorticotropin: circadian rhythm, dexamethasone suppression, and corticotropin-releasing hormone stimulation

The circadian rhythm, suppression with dexamethasone, and stimulation by corticotropin-releasing hormone (CRH) of plasma immunoreactive (IR) proopiomelanocortin N-terminal (NT) and IR-ACTH were studied in nine normal subjects and two patients with Addison's disease. The RIA for human NT (hNT) used was specific for NT except for partial cross-reactivity with gamma 2MSH. In normal subjects, plasma IR-hNT and IR-ACTH had almost parallel circadian rhythms and were suppressed by dexamethasone. The mean plasma levels of IR-hNT and IR-ACTH at 0800 h were 140 +/- 23 (SD) and 23 +/- 5 pg/ml, respectively. Plasma IR-hNT increased in parallel with IR-ACTH 15 to 30 min after iv injection of 100 micrograms ovine CRH. Maximum percent increases in plasma IR-hNT and IR-ACTH were 185 +/- 47 and 235 +/- 10%, respectively. In Addison's disease, on the other hand, plasma levels of IR-hNT and IR-ACTH were markedly elevated and the circadian rhythms were parallel. The mean plasma IR-hNT and IR-ACTH levels at 0900 h were 4363 and 1750 pg/ml, respectively. These results suggest that plasma hNT and ACTH are produced from a common precursor in the pituitary gland and secreted concomitantly under various physiological conditions such as stimulation by CRH and inhibition by glucocorticoid.     

The corticotropin-releasing hormone test in normal short children: comparison of plasma adrenocorticotropin and cortisol responses to human corticotropin-releasing hormone and insulin-induced hypoglycemia

The human corticotropin-releasing hormone (hCRH) tests were performed in twelve normal short children, and the responses of plasma ACTH and cortisol to iv administration of 1 micrograms/kg hCRH were compared with those to insulin-induced hypoglycemia. After administration of hCRH, the mean plasma ACTH level rose from a basal value of 3.3 +/- 0.4 pmol/l (mean +/- SEM) to a peak value of 9.2 +/- 0.8 pmol/l at 30 min, and the mean plasma cortisol level rose from a basal value of 231 +/- 25 nmol/l to a peak value of 546 +/- 30 nmol/l at 30 min. The ACTH response after insulin-induced hypoglycemia was greater than that after hCRH administration; the mean peak level (P less than 0.01), the percent maximum increment (P less than 0.01), and the area under the ACTH response curve (P less than 0.01) were all significantly greater after insulin-induced hypoglycemia than those after hCRH administration. Although the mean peak cortisol level after insulin-induced hypoglycemia was about 1.3-fold higher than that after hCRH administration (P less than 0.01), neither the percent maximum increment in plasma cortisol nor the area under the cortisol response curve after insulin-induced hypoglycemia was significantly different from that after hCRH administration. Consequently, the acute increases in plasma ACTH after the administration of 1 microgram/kg hCRH stimulated the adrenal gland to almost the same cortisol response as that obtained with a much greater increase in plasma ACTH after insulin-induced hypoglycemia. These results suggest that a plasma ACTH peak of 9-11 pmol/l produces near maximum acute stimulation of adrenal steroidogenesis.     

Diurnal variation in the response of plasma adrenocorticotropin and cortisol to intravenous ovine corticotropin-releasing hormone

To determine whether the plasma immunoreactive ACTH (IR-ACTH) and IR-cortisol responses to ovine corticotropin-releasing hormone (oCRH) depend on the time of day, we administered 1 microgram/kg BW synthetic oCRH as an iv bolus dose to five normal men at their usual time of awakening between 0530-0740 h, at 1600 h, and at 2300 h. Mean basal plasma IR-ACTH and IR-cortisol levels were highest upon awakening, intermediate at 1600 h, and lowest at 2300 h, reflecting the diurnal rhythm of ACTH secretion. There was no significant difference in the plasma IR-ACTH response to oCRH at different times of the day. In contrast, the mean maximum plasma IR-cortisol increment and mean integrated response were 2- and 2.6-fold greater (P less than 0.05), respectively, at 2300 h than upon awakening. In another study, oCRH was given in the morning (0700-0900 h) to 22 normal men and in the late afternoon (1600-1800 h) to 24 normal men. Mean basal plasma IR-ACTH and IR-cortisol levels were significantly higher (P less than 0.001) in the morning [24 +/- 3 pg/ml (mean +/- SEM) and 10.6 +/- 0.8 micrograms/dl, respectively] than in the afternoon (13 +/- 2 pg/ml and 5.6 +/- 0.6 micrograms/dl, respectively). Mean peak plasma IR-ACTH was slightly greater in the morning (60 +/- 5.5 pg/ml) than in the afternoon (47 +/- 5.5 pg/ml), the mean maximum plasma IR-ACTH increments were the same (35 +/- 4 and 34 +/- 5 pg/ml, respectively), and the mean integrated IR-ACTH response was slightly less in the morning (2036 +/- 414 vs. 2365 +/- 358 pg . min/ml), but none of these differences was statistically significant. Mean peak plasma IR-cortisol concentrations in the morning and afternoon were similar (18.7 +/- 0.7 and 17.3 +/- 0.9 micrograms/dl, respectively), but the mean maximum plasma IR-cortisol increments (8.1 +/- 0.8 and 11.7 +/- 0.9 micrograms/dl, respectively; P less than 0.005), and the mean integrated IR-cortisol responses (588 +/- 115 and 976 +/- 95 micrograms . min/dl, respectively; P less than 0.01) were greater in the afternoon. There was an inverse correlation between basal plasma IR-cortisol concentration and the integrated IR-ACTH response (P less than 0.05), the maximum IR-cortisol increment (P less than 0.001), and the integrated IR-cortisol response (P less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)     

Adrenal steroid, cortisol, adrenocorticotropin, and beta-endorphin responses to human corticotropin-releasing hormone stimulation test in normal children and children with premature pubarche

To determine whether CRH affects adrenal androgen, beta-endorphin (B-E), and ACTH secretion in normal children during sexual maturation, 17-hydroxyprogesterone (17-OHP), androstenedione (D4-A), dehydroepiandrosterone (DHEA), DHEA sulfate (DS), cortisol, B-E, and ACTH were measured after an iv injection of 1 microgram/kg human CRH. Children with premature pubarche were similarly analyzed to establish whether this condition is accompanied by altered hormonal responses to CRH. CRH produced consistent increases in ACTH, B-EP, and cortisol blood levels, which were comparable at all age intervals in all groups. 17-OHP increased after CRH injection, but its response linearly with age. D4-A levels were not influenced, while DHEA and DS levels were only partially influenced by CRH. The stimulated D4-A to 17-OHP ratio increased with sexual maturation, whereas ratios of cortisol to 17-OHP and D4-A to DHEA remained constant. Children with premature pubarche had hormonal responses similar in magnitude to those of prepubertal children of comparable age. In conclusion, an increase in 17,20-desmolase efficiency occurs with postnatal maturation after CRH challenge. Moreover, CRH does not appear to play an important role in premature pubarche.     

Prolactin-releasing peptide releases corticotropin-releasing hormone and increases plasma adrenocorticotropin via the paraventricular nucleus of the hypothalamus

Intracerebroventricular (ICV) injection of prolactin-releasing peptide (PrRP) is known to increase plasma adrenocorticotropin (ACTH) and cause c-fos expression in the hypothalamic paraventricular nucleus (PVN). We hypothesize that this is the site at which PrRP acts to increase plasma ACTH. We have used ICV injection and direct intranuclear injection of PrRP into the PVN to investigate the sites important in the stimulation of ACTH release in vivo. To investigate the mechanism of action by which PrRP increases ACTH, we have used primary culture of pituitary cells and measured neuropeptide release from in vitro hypothalamic incubations. ICV administration of PrRP increased plasma ACTH 10 min post-injection (PrRP 5 nmol 81.0 +/- 23.5 pg/ml vs. saline 16.8 +/- 14.1 pg/ml, p < 0.05). Intra-PVN injection of PrRP increased ACTH 5 min post-injection (PrRP 1 nmol 22.9 +/- 5.0 pg/ml vs. saline 10.3 +/- 1.4 pg/ml, p < 0.05). This effect continued until 40 min post-injection (PrRP 1 nmol 9.9 +/- 1.5 pg/ml vs. saline 6.2 +/- 0.5 pg/ml, p < 0.05). In vitro PrRP (1-100 nmol/l) did not effect basal or corticotropin-releasing hormone (CRH)-stimulated ACTH release from dispersed anterior pituitary cells. PrRP increased hypothalamic release of CRH (PrRP 100 nmol/l 1.4 +/- 0.2 nmol/explant vs. the basal 1.1 +/- 0.2 nmol/explant, p < 0.05) but not arginine vasopressin. PrRP also stimulated neuropeptide Y release (PrRP 100 nmol/l 56.5 +/- 11.8 pmol/explant vs. basal 24.0 +/- 1.9 pmol/explant, p < 0.01), a neuropeptide known to stimulate the hypothalamo-pituitary-adrenal axis. Our data suggest that in vitro PrRP does not have a direct action on the corticotrope but increases plasma ACTH via the PVN and this effect involves the release of hypothalamic neuropeptides including CRH and neuropeptide Y.     

Influences of corticotropin-releasing hormone, adrenocorticotropin, and cortisol on sleep in normal man

We studied the effects of the hormones of the hypothalamus-pituitary-adrenocortical axis on sleep processes in normal men. In one experiment, 10 men received placebo, cortisol (6 mg/h), and ACTH (0.55 U/h) as continuous iv infusions from 2200-0700 h on 3 separate nights. In another experiment, placebo and CRH (30 micrograms/h) were administered to another 10 men in the same manner. The mean plasma cortisol levels were comparable during the cortisol and ACTH infusions (552 vs. 668 nmol/L). During both infusions, the time spent in rapid eye movement (REM) sleep was significantly (P less than 0.01) reduced compared to that during the placebo infusion, and the cortisol infusion significantly (P less than 0.05) enhanced the time spent in slow wave sleep (SWS). The CRH dose used only moderately increased plasma ACTH and cortisol levels; the changes in SWS and REM sleep during CRH infusion were in the same direction as occurred during the cortisol infusion, but were not significant. These results suggest that cortisol has a sleep modulatory effect. The decrease in REM sleep during the ACTH infusion may be mediated by the rise in endogenous cortisol. However, ACTH specifically altered sleep, in that it inhibited the cortisol-induced increase in SWS. Peripherally administered CRH had no intrinsic influence on sleep.     

Differential plasma beta-endorphin, beta-lipotropin, and adrenocorticotropin responses to stress in rats

This study was designed to compare the amounts of ACTH, beta-endorphin (beta END), and beta-lipotropin (beta LPH) that are present in plasma under basal conditions and after single and repeated administration of a discrete 2-min restraint stress both in intact and in chronically adrenalectomized rats. In intact rats, application of a 2-min restraint stress produced rapid parallel increases in plasma concentrations of radioimmunoassayable ACTH and beta END/beta LPH (the total of beta END-like immunoreactivities), with peaks 2.5-5 min after onset of the stress and return almost to basal concentrations by 30 min. Gel exclusion chromatography [Sephadex G-50 (fine)] and subsequent RIA revealed that plasma obtained from control nonstressed intact rats contained much greater quantities of beta END (94% of the total beta END/beta LPH immunoreactivity) than beta LPH. In contrast, equal amounts of beta END and beta LPH were present in plasma of intact rats 2.5-10 min after onset of the 2-min restraint stress. Chronically adrenalectomized rats lacking glucocorticoid-negative feedback had significantly higher basal plasma concentrations of beta END/beta LPH and ACTH than those present in intact rats. Furthermore, the plasma responses of both beta END/beta LPH and ACTH to stress were markedly enhanced in chronically adrenalectomized rats compared to the corresponding responses in intact rats. Gel exclusion chromatography revealed that both the higher basal concentration and the enhanced plasma beta END/beta LPH response to stress in adrenalectomized rats resulted primarily from increases in the beta LPH component, with lesser increases in the beta END component. In contrast to the proportion in intact rats, in chronically adrenalectomized rats, beta END represented about 27% of the total beta END/beta LPH immunoreactivity in the basal state and about 18% 5-10 min after the onset of restraint stress. In intact rats, the plasma ACTH responses to a subsequent stress applied 5 min (a time when peak plasma levels of hormones are present) or 30 min (a time when the plasma hormone concentrations have returned to prestress levels) after the initial stress and the plasma beta END/beta LPH response to a second stress applied at 30 min were equal to the corresponding hormone responses to a single stress. In contrast, the plasma beta END/beta LPH response to the subsequent stress applied 5 min after the initial stress was significantly potentiated in intact rats.(ABSTRACT TRUNCATED AT 400 WORDS)     

Prolactin stimulates rat hypothalamic corticotropin-releasing hormone and pituitary adrenocorticotropin secretion in vitro.

In rats hyperprolactinemia increases corticotropin-releasing hormone (CRH) concentration and secretion in hypophysial portal blood and the serum concentration of adrenocorticotropic hormone (ACTH). To determine whether the stimulatory effect of prolactin (PRL) on CRH and ACTH in vivo is exerted directly on the hypothalamus, hypothalamic explants and primary anterior pituitary cell cultures from adult male and female rats were used. Hypothalami explanted from male and female rats were preincubated during 90 min and treated for 30 min with rat PRL (rPRL) at concentrations of 10(-8), 10(-7), and 10(-6) M (about 200, 2,000, and 20,000 ng/ml, respectively), corticosterone at concentrations of 10(-7), 10(-6), and 10(-5) M (about 35,350 and 3,500 ng/ml, respectively), ACTH at concentrations ranging from 10(-10) to 10(-7) M (0.46, 4.6, 46, and 460 ng/ml, respectively), and graded concentrations of testosterone or estradiol. Concentrations of immunoreactive CRH (iCRH) were measured by radioimmunoassay. rPRL at 10(-6) M stimulated iCRH secretion by 360 and 400% of the basal iCRH output (about 14 pg/hypothalamus), respectively, from hypothalami explanted from male and female rats. ACTH and corticosterone did not suppress rPRL (10(-6) M) induced iCRH secretion. Corticosterone at the concentration of 10(-6) M potentiated rPRL (10(-6) M) induced iCRH secretion in hypothalami explanted from male, but not female rats. Gonadal steroids had no effect either on the basal or rPRL (10(-6) M) stimulated iCRH secretion, with the exception of estradiol which augmented the response to 10(-6) M rPRL by about fivefold, but only at the concentration of 10(-8) M (about 2.7 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Adrenergic modulation of adrenocorticotropin responses to insulin-induced hypoglycemia and corticotropin-releasing hormone

To study possible adrenergic modulation of pituitary-adrenal responses to insulin-induced hypoglycemia and CRH we examined the effect of nonselective alpha-blockade (phentolamine) and nonselective beta-blockade (propranolol) on plasma ACTH, cortisol, and vasopressin (AVP) responses to hypoglycemia and CRH in five normal men. Infusion of propranolol or phentolamine did not alter basal plasma ACTH or cortisol levels. The propranolol infusion enhanced the stimulatory effect of hypoglycemia on ACTH, cortisol, and AVP secretion and also enhanced the stimulatory effect of CRH on ACTH and cortisol secretion. Infusion of phentolamine inhibited hypoglycemia-induced ACTH and AVP secretion, but had no effect on the stimulatory effect of CRH on ACTH and cortisol secretion. The increments of plasma ACTH and cortisol induced by an almost maximal dose of CRH (1 microgram/kg) were smaller than those induced by hypoglycemia. The propranolol-induced enhancement of the ACTH response to hypoglycemia was almost the same as the ACTH response to CRH alone. From these results we conclude that propranolol may act at the pituitary level to enhance CRH action, rather than AVP action, and that the ACTH response to hypoglycemia may be mediated by hypothalamic alpha-adrenergic activation.     

Presence of immunoreactive gamma-melanocyte-stimulating hormone, adrenocorticotropin, and beta-endorphin in human gastric antral mucosa

gamma MSH-like, ACTH-like, and beta-endorphin-like immunoreactivities (gamma MSH-LI, ACTH-LI, and beta-endorphin-LI, respectively) were detected in water extracts of four human gastric antral mucosa. The concentrations of gamma MSH-LI, ACTH-LI, and beta-endorphin-LI in the boiling water extracts were 9.9 +/- 3.3, 6.2 +/- 1.8, and 3.9 +/- 1.3 ng/g (mean +/- SE), respectively. Gel exclusion chromatography on a Bio-Gel P-60 column showed that most ACTH-LI and beta-endorphin-LI were eluted at the elution positions of human ACTH and beta-endorphin, respectively. The major peak of gamma MSH-LI was eluted at the elution position of big gamma MSH-LI, but another peak was eluted at the elution position of small gamma MSH-LI, as in bovine intermediate pituitary. Concanavalin A-agarose affinity chromatography showed that 52% of gamma MSH-LI was specifically bound to the column, but only 8% of ACTH-LI and none of beta-endorphin-LI were specifically bound. These results suggest that there exists an ACTH/beta-lipotropin common precursor protein in human antral mucosa and that the processing of the precursor is accelerated as a bovine intermediate pituitary, indicating possible roles of these peptides in the function of the gastrointestinal tract.     

Cerebrospinal fluid immunoreactive corticotropin-releasing hormone and adrenocorticotropin secretion in Cushing's disease and major depression: potential clinical implications.

To explore whether possible differences in central nervous system neuromodulators contribute to the differential presentation of affective symptomatology in Cushing's disease and major depression, we examined the levels of immunoreactive CRH and ACTH in the cerebrospinal fluid (CSF) of 11 patients with Cushing's disease, a patient with ectopic ACTH secretion, 34 patients with major depression, and 60 healthy subjects. We elected to measure these peptides not only because both are classically involved in pituitary-adrenal regulation, but also because their primarily arousal-producing and anorexigenic behavioral effects in experimental animals suggest that they may play a role in the symptom complex of depressive syndromes. We also explored whether the CSF levels of these peptides were more helpful in determining the often difficult differential diagnosis between major depression and Cushing's disease than the plasma ACTH response to ovine CRH, a currently used but somewhat insensitive laboratory means of distinguishing these disorders. CSF levels of immunoreactive CRH and ACTH were significantly lower in Cushing's disease patients [21.9 +/- 2.7 and 15.4 +/- 1.8 pg/mL, (mean +/- SEM), respectively] compared to patients with major depression [38.4 +/- 2.3 pg/mL (P less than 0.01) and 24.5 +/- 1.6 pg/mL (P less than 0.01), respectively] and controls [38.4 +/- 1.6 pg/mL (P less than 0.001) and 26.3 +/- 1.1 pg/mL (P less than 0.001), respectively]. The coexistence of high plasma ACTH and low CSF ACTH in Cushing's disease yielded a CSF/plasma ACTH ratio consistently less than that in depressed patients, with only 2 of 31 subjects comprising both groups showing values that overlapped. In contrast, 9 of the combined patients showed ACTH responses to ovine CRH that overlapped. These data suggest that differences in centrally directed CRH secretion may account for the differential presentation of the dysphoric syndromes seen in major depression and Cushing's disease. Hence, the classic form of major depression (melancholia), is often associated with evidence of pathological hyperarousal, such as intense anxiety, sleeplessness, and anorexia, while that of Cushing's disease is associated with evidence of pathological hyperarousal, including hyperphagia, fatigue, and inertia. Moreover, measurement of the CSF/plasma ACTH ratio may serve as a clinically useful adjunct to the ovine CRH stimulation test and other laboratory measures in determining the differential diagnosis between major depression and Cushing's disease.     

Secretion of adrenocorticotropin, beta-endorphin and calcitonin by cultured medullary thyroid carcinoma cells. Effects of synthetic corticotropin-releasing factor and lysine vasopressin

The present study was performed to investigate the potential of human medullary thyroid carcinoma (MTC) cells to secrete ACTH, beta-LPH/beta-EP. In addition, these studies might shed further light on the possible synthesis of a common precursor molecule for calcitonin (CT), ACTH and beta-LPH/beta-EP. MTC tissue was obtained from 10 patients (6 familial, 4 sporadic) without clinical and biochemical signs of Cushing's syndrome. Single cell suspensions were cultured for 1 to 2 weeks. Mean basal release of beta-LPH/beta-EP was 0.76 +/- 0.29 (SE) ng/10(6) cells/4 h (n = 10). Dibutyryl cyclic AMP (3 mM) stimulated beta-EP release significantly in 3 out of 7 cultures, while Ca2+ (2 mM) had no effect at all. The effects of the physiological regulators of pituitary ACTH and beta-LPH/beta-EP secretion, synthetic corticotropin-releasing factor (CRF-41) and vasopressin (LVP) were also studied in these MTC cell cultures. LVP (100 nM) had no effect on beta-EP release from MTC cells of all 8 cultures investigated. CRF-41 (10 nM) stimulated beta-EP release from 5 cultures and was without effect on 4. Maximal stimulation was noticed with 10 nM, while the effect of 100 nM CRF-41 was lower or absent. Stimulation was most outspoken in 3 cultures of familial MTC, whereas in 2 cultures of sporadic MTC CRF-41 stimulated beta-EP release marginally only after a 24 h incubation. LVP and/or CRF-41 stimulated CT release significantly in 3 cultures from sporadic MTC, while in these cultures the effect of CRF-41 on beta-EP release was either very small or absent.(ABSTRACT TRUNCATED AT 250 WORDS)