Biomedical subjects

W E Nicholson

Publications and source records attributed to W E Nicholson.

At least 19 recordsLinked to original sources

PubMed1995

Factitious hypercortisoluria.

A case of factitious hypercortisoluria due to the presumed addition of glucocorticoid to the urine collections is presented. The discrepancy between urine and blood steroid hormone levels first suggested that the patient had tampered with the urine collections. Plasma steroid hormone levels were normal, whereas the urinary free cortisol level fluctuated in a totally random fashion. Urinary 17-hydroxycorticosteroid and urinary free corticosterone levels were normal. Partition chromatography of the urine indicated that the cortisol immunoactivity coeluted with authentic cortisol. This study illustrates the value of multiple urinary and plasma steroid determinations, especially urinary or plasma corticosterone measurements, in suspected cases of factitious Cushing's syndrome.

Adrenal Cortex Hormones↗

PubMed1994

A sensitive radioimmunoassay for fludrocortisone in human plasma.

Fludrocortisone has been a mainstay of therapy for orthostatic hypotension for many years. Clinical experience suggests that there exists a substantial interindividual variation in responsiveness to the drug. To assess this, we have developed an assay that permits measurement of the low concentrations of fludrocortisone found in human plasma. Fludrocortisone was detected by radioimmunoassay. A polyclonal rabbit antibody, raised against dexamethasone which cross-reacts strongly with fludrocortisone, was reacted with either standard or unknown samples in the presence of [125I]fludrocortisone-3-TyrNH2 (synthesized by coupling tyrosine amide to fludrocortisone-3-oxime and iodinating with chloramine T oxidation). The ED10, ED50, and ED80 were 0.34, 5.0, and 30 ng/mL of plasma, respectively. The cross reactivity with other 9-fluorinated steroids was found as follows: dexamethasone, 340%; betamethasone, 230%; and triamicinolone, 8%. To preclude an erroneous result, subjects who were pregnant or receiving any steroid medication were excluded from the study. The percent cross-reactivity with the main naturally occurring steroids was as follows: 11-desoxycortisol 3.2%, cortisol 1.1%, DOC 0.3%, pregnenolone 0.1%, corticosterone 0.06%, progesterone 0.05%, and aldosterone < 0.05%. The only compound with potential for interference, because of its high level in the circulation in the early morning, was cortisol.(ABSTRACT TRUNCATED AT 250 WORDS)

Fludrocortisone↗

PubMed1994

Concentrations of corticotropin-releasing hormone, norepinephrine, MHPG, 5-hydroxyindoleacetic acid, and tryptophan in the cerebrospinal fluid of alcoholic patients: serial sampling studies.

Abnormalities in corticotropin-releasing hormone (CRH) secretion, noradrenergic neurotransmission, and serotonergic activity in the central nervous system (CNS) have all been hypothesized to exist in alcoholic patients, as have abnormalities in hypothalamic-pituitary adrenal function. To test these hypotheses, we continuously sampled cerebrospinal fluid (CSF) from alcoholic patients after 38-124 days of abstinence and from normal volunteers via a flexible, indwelling lumbar subarachnoid catheter and measured CRH, norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG), tryptophan, and 5-hydroxyindoleacetic acid (5-HIAA) concentrations at 10-min intervals, from 11:00 through 17:00 h. The spinal canal catheter was inserted at approximately 08:00 h. Serial plasma ACTH, cortisol, and NE concentrations were also measured. A mixed liquid meal was consumed at 13:00 h. CSF CRH concentrations were lower in alcoholic patients than in normal volunteers (26 +/- 15 vs. 60 +/- 30 pg/ml, respectively, p < 0.05 by ANOVA), as were CSF NE levels (0.33 +/- 0.09 vs. 1.15 +/- 0.51 pmol/ml, respectively, p < 0.01). Plasma NE and CSF MHPG levels were normal in the alcoholic patients. CSF tryptophan and 5-HIAA and plasma ACTH and cortisol concentrations did not differ between the groups. These studies extend our finding of reduced spinal canal CSF CRH concentrations in depressed patients to abstinent chronic alcoholics.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1993

Cholecystokinin in human cerebrospinal fluid: concentrations, dynamics, molecular forms and relationship to fasting and feeding in health, depression and alcoholism.

Very little is known about the physiologic significance of the gut-brain hormone cholecystokinin (CCK) in the human central nervous system, although the hormone has been hypothesized to be involved in the regulation of both appetite and anxiety. We continuously collected lumbar cerebrospinal fluid (CSF) via indwelling subarachnoid catheters in ten normal volunteers, ten patients with major depression and five abstinent alcoholic humans, while fasting and after eating. Five other healthy subjects were fasted throughout the experiment. We quantified CSF immunoreactive cholecystokinin (IR-CCK) and glucose concentrations at 10-min intervals from 11.00 to 17.00 h. No difference in CSF IR-CCK concentration, half-life or rhythm was observed between normal volunteers and either depressed or alcoholic patients. Fasting CSF IR-CCK concentrations were 1.3 +/- 0.18, 1.3 +/- 0.21 and 1.2 +/- 0.21 fmol/ml (mean +/- S.E.M.) in normal volunteers, depressed patients and alcoholic patients, respectively. After eating, CSF IR-CCK concentrations rose to 1.5 +/- 0.21, 1.5 +/- 0.24 and 1.4 +/- 0.26 fmol/ml, respectively. Normal volunteers who did not eat had similar basal CSF IR-CCK concentrations (1.1 +/- 0.1 fmol/ml) which similarly rose to 1.4 +/- 0.13 fmol/ml during the sampling interval. In contrast, CSF glucose concentrations rose only in the subjects who ate, beginning to rise after about 1 h and remaining elevated for at least 3 h after eating. These data suggest the existence of a diurnal rhythm of IR-CCK release into CSF, as opposed to a response to feeding. The disappearance half-time of CCK in human CSF is less than 13 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Chromogranin A does not mediate glucocorticoid inhibition of adrenocorticotropin secretion.

It has recently been proposed that chromogranin A (CgA), a 50-kilodalton acidic glycoprotein that is costored and cosecreted with hormones and neurotransmitters in a variety of tissues, mediates glucocorticoid inhibition of ACTH secretion from AtT20/D16v mouse anterior pituitary corticotroph tumor cells by an undefined autocrine mechanism. We used AtT20/D16v cells, RIAs for murine CgA and ACTH, complementary DNA probes for CgA and POMC, the precursor of ACTH, antiserum that reacts with murine CgA, highly purified bovine CgA, and synthetic rat and porcine pancreastatin, a bioactive cleavage product of CgA in some systems, to study the kinetics of the effect of glucocorticoids on CgA and ACTH synthesis and secretion and of CgA's subsequent effects on ACTH secretion. Exposure to 100 nM dexamethasone (DEX) did not alter the size of CgA or POMC messenger RNA (mRNA) transcripts but increased cell CgA mRNA content 42% by 3 h and 192% by 48 h. DEX decreased cell POMC mRNA content 22% by 6 h and 57% by 48 h. These divergent effects of DEX on steady state mRNA levels were accompanied by similar divergent effects on the production of CgA and ACTH protein. Thirty-minute exposure to 10 nM ovine CRF increased CgA and ACTH release to 300% and 360% of basal levels, respectively. One-hour DEX pretreatment inhibited CRF-stimulated CgA and ACTH release 58% and 49% at 30 min and 67% and 66% at 60 min, respectively. There was a positive correlation between CgA and ACTH release under all conditions at both times (r = 0.976 and 0.964, respectively, P < 0.001), consistent with costorage and cosecretion of the two proteins. The ratio of secreted ACTH to CgA decreased progressively with DEX treatment. Purified bovine CgA (100 nM) had little or no effect on basal or CRF-stimulated ACTH secretion from AtT20/D16v cells, 100 nM synthetic pancreastatin had no significant effect on basal or CRF-stimulated ACTH release from AtT20/D16v cells or dispersed normal male rat anterior pituitary cells, and anti-CgA sera had no significant effect on basal or CRF-stimulated ACTH release from AtT20/D16v cells. These results indicate: 1) that DEX stimulates CgA synthesis, whereas it inhibits POMC synthesis; 2) that CgA and ACTH are cosecreted; 3) that DEX increases CgA secretion relative to ACTH secretion, but decreases the absolute secretion of both proteins; and 4) that neither CgA nor its proteolytic product, pancreastatin, inhibits ACTH secretion. Thus, CgA does not mediate the inhibitory effect of DEX on ACTH secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗

PubMed1993

Effect of protein kinase-C depletion on inositol trisphosphate-mediated and cyclic adenosine 3',5'-monophosphate-dependent protein kinase-mediated adrenocorticotropin secretion.

We studied the effect of Ca2+/phospholipid-dependent protein kinase-C (protein kinase-C) down-regulation by chronic exposure to phorbol 12-myristate 13-acetate (PMA) on ACTH secretion by dispersed male rat anterior pituitary cells in a microperifusion system. Preincubation for 24 h and preperifusion for 3 h with 0.1 and 1 microM PMA significantly inhibited (by 85% and 91%, respectively) the specific cell binding of [3H]phorbol 12,13-dibutyrate, an index of protein kinase-C concentration, and significantly reduced (by 101% and 20%, respectively) the sustained plateau (final 15-min) phase of the ACTH response to arginine vasopressin (AVP) and (by 56% and 54%, respectively) the sustained (full 20-min) response to dioctanoylglycerol (DOG), both of which are mediated by protein kinase-C activation. In contrast, the spike (initial 5-min) phase of the response to AVP, which is mediated by intracellular Ca2+ release from inositol 1,4,5-trisphosphate (InsP3)-sensitive stores, was significantly increased (by 112% and 99%, respectively), but the spike-type response to ionomycin, which releases intracellular Ca2+ by an InsP3-independent mechanism, was unaffected. AVP significantly stimulated inositol bisphosphate and InsP3, but not inositol monophosphate, accumulation, and PMA pretreatment significantly enhanced their AVP-stimulated accumulation (by 86%, 34%, and 78%, respectively), an effect that was abolished by simultaneous preperifusion with PMA and cycloheximide to inhibit new protein synthesis. Enhancement of the spike phase response to AVP and AVP-stimulated InsP3 accumulation were lost within 1 h of PMA removal, but [3H]phorbol 12,13-dibutyrate binding and the sustained responses to AVP and DOG remained suppressed after 3 h. Pretreatment with 0.1 and 1 microM PMA slightly reduced the sustained responses to CRF (by 29% and 16%, respectively) and 8-bromo-cAMP (by 8% and 12%, respectively), which are mediated by protein kinase-A activation and extracellular Ca2+ influx via L-type voltage-sensitive Ca2+ channels, but not the response to KCl, which is mediated by extracellular Ca2+ influx via all types of voltage-sensitive Ca2+ channels. The sustained response to CRF was still suppressed 1 h after PMA removal, but returned to the control level by 3 h. When new protein synthesis was inhibited by preperifusion with cycloheximide alone for 3 h after 24-h PMA pretreatment, recovery from the effects of PMA was abolished. Three-hour exposure to cycloheximide without PMA pretreatment inhibited the sustained responses to CRF, AVP, and DOG, but not the spite response to AVP.(ABSTRACT TRUNCATED AT 400 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1992

Lymphocyte-derived adrenocorticotropin is insufficient to stimulate adrenal steroidogenesis in hypophysectomized rats.

Cells of the immune system can produce and respond to peptide hormones associated with the endocrine system. However, the physiological significance of these endocrine-immune interactions is not known. It has been postulated that cells of the immune system, when stimulated with viruses that induce interferon-alpha, produce sufficient levels of ACTH to stimulate adrenal steroidogenesis and, thus, function as an auxiliary source of ACTH that may have a role in the response to stress. However, we have confirmed that levels of ACTH-related peptides produced by immunocompetent cells are far lower than those produced by the pituitary, raising questions about the ability of lymphocyte-derived ACTH to stimulate adrenal function. Furthermore, we have rigorously examined this issue using intact and hypophysectomized rats treated with Newcastle disease virus. Although high levels of interferon-alpha were produced by both intact and hypophysectomized rats, and the plasma corticosterone concentration increased dramatically in intact animals, corticosterone remained undetectable in hypophysectomized rats. The lack of a corticosterone response in these animals was not due to adrenal insensitivity to ACTH, as shown by a normal rise in corticosterone following Cosyntropin injection 8 h after hypophysectomy. The findings demonstrate that levels of ACTH produced by nonpituitary sources in response to viral infection are not sufficient to stimulate adrenal steroidogenesis.

Adrenal Cortex Hormones↗

PubMed1991

Adrenocorticotropin stimulation test: effects of basal cortisol level, time of day, and suggested new sensitive low dose test.

Adrenal response to iv administration of 1-24 ACTH (250 micrograms) was examined in normal volunteers under various conditions. The effect of basal cortisol levels was examined by performing the tests at 0800 h with and without pretreatment with dexamethasone. The effect of time of day was evaluated by performing the tests at 0800 h and at 1600 h, eliminating possible basal cortisol influence by pretreatment with dexamethasone. In the first set of tests, despite significantly different baseline levels, 30-min cortisol levels were not different (618 +/- 50 vs. 590 +/- 52 nmol/L). Afternoon cortisol levels in response to ACTH were found to be significantly higher than morning levels at 5 min (254 +/- 50 vs. 144 +/- 36 nmol/L, p less than 0.01) and at 15 min (541 +/- 61 vs. 433 +/- 52 nmol/L, p less than 0.02). This difference in response was no longer notable at 30 min (629 +/- 52 and 591 +/- 52 nmol/L). We tried also to determine the lowest ACTH dose which will elicit a maximal cortisol response. No difference was found in cortisol levels at 30 and 60 min in response to 250 and 5 micrograms 1-24 ACTH. Using 1 micrograms ACTH, the 30-min response did not differ from that to 250 micrograms (704 +/- 72 vs. 718 +/- 55 nmol/L, respectively). However, the 60-min response to 1 microgram was significantly lower (549 +/- 61 vs. 842 +/- 110 nmol/L, p less than 0.01). Using this low dose ACTH test (1 microgram, measuring 30-min cortisol level), we were able to develop a much more sensitive ACTH test, which enabled us to differentiate a subgroup of patients on long-term steroid treatment who responded normally to the regular 250 micrograms test, but had a reduced response to 1 microgram. The stability of 1-24 ACTH in saline solution, kept at 4 C, was checked. ACTH was found to be fully stable after 2 hs in a concentration of 5 micrograms/ml in glass tube and 0.5 micrograms/ml in plastic tube. It was also found to be fully stable, both immunologically and biologically, for 4 months, under these conditions. We conclude that the 30-min cortisol response to ACTH is constant, unrelated to basal cortisol level or time of day. It is therefore the best criterion for measuring adrenal response in the short ACTH test. The higher afternoon responses at 5 and 15 min suggest greater adrenal sensitivity in the afternoon, but further studies are needed to clarify this issue.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1990

Role of protein kinase-C in the adrenocorticotropin secretory response to arginine vasopressin (AVP) and the synergistic response to AVP and corticotropin-releasing factor by perifused rat anterior pituitary cells.

Arginine vasopressin (AVP) stimulates biphasic release of ACTH from anterior pituitary corticotrophs. The response consists of an initial transient spike phase lasting less than 3 min and a subsequent sustained plateau phase that persists for as long as AVP is present. AVP also acts synergistically with CRF on ACTH release. We have previously shown that the initial spike phase of the response mainly requires release of intracellular Ca2+ and is independent of calmodulin, whereas the sustained plateau phase, like the monophasic sustained response elicited by CRF, involves the influx of extracellular Ca2+ via L-type voltage-sensitive Ca2+ channels and activation of calmodulin. We have also shown that the synergism between AVP and CRF does not require extracellular Ca2+ influx. In this study we examined the role of Ca2+/phospholipid-dependent protein kinase-C (PKC) in the two phases of the response to AVP and in the synergism between AVP and CRF. We exploited the observation that prolonged exposure to phorbol esters down-regulates PKC. Dispersed adult male rat anterior pituitary cells were incubated in static suspension culture for 4-5 days, 0.5 microM phorbol 12-myristate 13-acetate (PMA) or 0.0005% dimethylsulfoxide vehicle alone was added, and the incubation was continued for 24 h. The cells were preperifused with PMA-free perifusion medium for 3 h and then perifused with various agents for 10-20 min. Effluent fractions were collected every 30 sec or 1 min and subjected to ACTH RIA. Pretreatment with PMA inhibited the subsequent response to 100 nM PMA and 100 microM dioctanoylglycerol, but not to 5 microM forskolin or to depolarization with 56 mM KCl, demonstrating specific down-regulation of PKC. PMA pretreatment had no effect on the initial spike phase of the response to AVP, but inhibited the sustained plateau phase by 57% (P less than 0.005) and, consequently, the integrated total response by 33% (P less than 0.05). Pretreatment had no effect on the response to CRF. However, pretreatment with PMA completely blocked both phases of the synergistic response to the combination of AVP and CRF. These results indicate that activation of PKC is required for the sustained phase of the response to AVP and both phases of its synergistic interaction with the protein kinase-A pathway, but is not involved in the initial spike phase of the response to AVP, which presumably is mediated by inositol 1,4,5-trisphosphate-stimulated mobilization of intracellular Ca2+, or in the independent activation of the protein kinase-A pathway by CRF.

Adrenocorticotropic Hormone↗

PubMed1988

Immunoreactive proopiomelanocortin (POMC) peptides and POMC-like messenger ribonucleic acid are present in many rat nonpituitary tissues.

Immunoreactive (IR) POMC peptides have been found in several rat nonpituitary tissues. We found IR-ACTH, IR-beta-endorphin (beta END), and IR-gamma MSH in extracts from the following eight rat nonpituitary tissues, listed in order of decreasing POMC peptide concentrations: testis, duodenum, kidney, colon, liver, lung, stomach, and spleen, but not in adrenal or muscle extracts. Concentrations were very low and ranged from less than 0.00003% to 0.0005% of pituitary levels. In testis, duodenum, and colon, IR-gamma MSH and IR-beta END concentrations were only 5-37% of IR-ACTH levels. Gel filtration chromatography showed that IR-ACTH and IR-beta END coeluted in a major peak of 15,000 daltons, which is slightly larger than expected for a C-terminal peptide containing rat ACTH and beta-lipotropin. There were also a minor higher mol wt peak of IR-ACTH and IR-beta END and a minor IR-beta END peak that eluted in the position of mature beta END. There was no peak of IR-ACTH that corresponded to the size of mature ACTH. To determine whether these nonpituitary tissues also contained a POMC-like mRNA, which would confirm that the peptides were synthesized locally within the tissues, we examined poly(A) RNA prepared from 10 nonpituitary tissues and total RNA from pituitary by Northern blot hybridization for the presence of a POMC-like mRNA with an exon 3 riboprobe. Pituitary contained a single POMC mRNA species of about 1000 nucleotides. A short POMC-like mRNA of about 800 bases was found in all nonpituitary tissues, except spleen and muscle. Compared to POMC mRNA levels in pituitary, the concentration of POMC-like mRNA was 0.5% in testis and 0.03-0.07% in the other tissues. The ratio of POMC-like mRNA to IR-POMC peptide concentrations in nonpituitary tissues was at least 1000 times greater than that in the pituitary. We conclude that the POMC gene is expressed in many nonpituitary tissues and that either the short POMC-like mRNA is translated much less efficiently or POMC peptides are released or degraded much more rapidly in nonpituitary tissues than in the pituitary.

Adrenocorticotropic Hormone↗

PubMed1988

Proopiomelanocortin gene is expressed in many normal human tissues and in tumors not associated with ectopic adrenocorticotropin syndrome.

Immunoreactive (IR) POMC peptides have been detected in several human nonpituitary tissues and most pheochromocytomas and lung cancers, including those not associated with ectopic ACTH syndrome. We found IR-ACTH, IR-gamma MSH, IR-beta-endorphin (beta END), and IR-lipotropin in extracts from the following 10 normal human tissues, listed in order of decreasing POMC peptide concentrations: adrenal, testis, spleen, kidney, ovary, lung, thyroid, liver, colon, and duodenum. IR-ACTH, IR-gamma MSH, and IR-beta END were detected in all six pheochromocytomas and all 12 lung tumors (six squamous cell carcinomas, five adenocarcinomas, and one small cell carcinoma) we examined, as well as in a squamous cell carcinoma of the larynx. None of the patients had clinical evidence of ectopic ACTH syndrome. To determine whether these nonpituitary tissues and tumors actually synthesize POMC, rather than simply absorb POMC peptides from plasma, we examined poly(A) RNA prepared from these tissues and total RNA from pituitary by Northern blot hybridization for the presence of POMC-like mRNA with an exon 3 riboprobe. Pituitary contained a single POMC mRNA species of about 1150 bases. A short POMC-like mRNA of about 900 bases was found in all normal nonpituitary tissues, three of five pheochromocytomas, eight of nine lung cancers, and the laryngeal squamous cell tumor. In addition, larger POMC-like mRNA species between 1200 to 1500 bases were detected in adrenal, testis, ovary, placenta, two pheochromocytomas, and three squamous cell lung tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗

PubMed1988

Increased pro-opiomelanocortin-derived peptide release in myotonic dystrophy.

The response of plasma immunoreactive (IR)-ACTH, IR-beta-endorphin (beta-END) and IR-cortisol to insulin-induced hypoglycaemia, an acute stimulus to the pituitary corticotrophs through the central nervous system, and to synthetic ovine corticotrophin-releasing hormone (CRH), a direct corticotroph stimulator, were studied in normal males and males with myotonic dystrophy. Myotonics had an increased IR-ACTH and IR-beta-END response to hypoglycaemia and an increased IR-ACTH response to CRH compared with normals. Plasma IR-cortisol response were not different in either group of subjects to both stimuli. This neuroendocrine abnormality in myotonic dystrophy may represent a manifestation of the purported specific cell membrane defect underlying the disease. This is the first report of an abnormality in proopiomelanocortin peptide release in myotonic dystrophy.

Adolescent↗

PubMed1987

Pituitary and hypothalamic hormones in normal and neoplastic adrenal medullae: biologically active corticotropin-releasing hormone and corticotropin.

Six normal and 8 neoplastic adrenal medullae were assayed for several immunoreactive (IR) proopiomelanocortin (POMC) and hypothalamic peptides. IR-POMC peptides were found in normal and tumor tissue in concentrations ranging from 0.0003 to 0.1% of those in pituitary. Their molecular sizes resembled those of pituitary intermediate lobe POMC peptides. No intact POMC was found. One pheochromocytoma contained fully bioactive IR-adrenocorticotropic hormone (IR-ACTH; Mr approximately 4,500) and an intermediate-sized (Mr approximately 10,000) IR-ACTH with approximately 69% bioactivity. Normal and tumorous medullae contained IR-corticotropin-releasing hormone (CRH) in concentrations ranging from 0.6 to 4% of those in hypothalamus except for one pheochromocytoma that contained 40 times that amount of IR-CRH, which was chromatographically indistinguishable from hypothalamic CRH and fully bioactive. IR-somatostatin and IR-growth hormone-releasing hormone were found in both tissue types, but IR-gonadotropin-releasing hormone and IR-thyrotropin-releasing hormone (TRH) were not, although IR-histidyl-proline diketopiperazine, a putative TRH metabolite, was found. IR-arginine vasopressin was found in two normal medullae, but not in pheochromocytomas.

Adrenal Gland Neoplasms↗

PubMed1987

Corticotropin-releasing hormone: stimulation of ACTH secretion in normal man.

Synthetic ovine corticotropin-releasing hormone (oCRH) is a potent and specific ACTH secretagogue in man. Threshold and maximal i.v. doses are 0.01-0.03 and 3-10 micrograms/kg or less, but increase in frequency, severity, and duration at higher doses. oCRH produces a biphasic plasma immunoreactive (IR)-ACTH response and has a prolonged duration of action that is probably due to its long circulating half-life. Other pro-opiomelanocortin IR-peptide are secreted concomitantly in equimolar amounts. Plasma IR-cortisol concentration tends to follow that of ACTH, but also reflects cortisol's longer circulating half-life and the fact that acutely the maximally-stimulating plasma IR-ACTH level is about 45 pg/ml. oCRH is as effective given s.c. as i.v., but intranasal administration is only 1% as effective. Sex and age have no effect on the plasma IR-ACTH and IR-cortisol responses to oCRH. The time of day of oCRH administration has little influence on the plasma IR-ACTH response, but the plasma IR-cortisol response is much greater to oCRH given later in the day than early in the morning. Plasma IR-ACTH response to oCRH is more dependent on the basal plasma IR-cortisol level than the time of day. Arginine vasopressin given at the same time as oCRH potentiates 4-fold the plasma IR-ACTH response to oCRH alone, almost to levels obtained with insulin-induced hypoglycemia. However, oCRH administered at the onset of insulin-induced hypoglycemia does not cause higher plasma IR-ACTH levels, indicating that endogenous CRH levels are maximally-stimulating during the hypoglycemic response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1986

Prokaryotic adenylate cyclase toxin stimulates anterior pituitary cells in culture.

Bordetella pertussis synthesizes a variety of virulence factors including a calmodulin-dependent adenylate cyclase (AC) toxin. Treatment of anterior pituitary cells with this AC toxin resulted in an increase in cellular cAMP levels that was associated with accelerated exocytosis of growth hormone (GH), prolactin, adrenocorticotropic hormone (ACTH), and luteinizing hormone (LH). The kinetics of release of these hormones, however, were markedly different; GH and prolactin were rapidly released, while LH and ACTH secretion was more gradually elevated. Neither dopamine agonists nor somatostatin changed the ability of AC toxin to generate cAMP (up to 2 h). Low concentrations of AC toxin amplified the secretory response to hypophysiotrophic hormones. We conclude that bacterial AC toxin can rapidly elevate cAMP levels in anterior pituitary cells and that it is this response that explains the subsequent acceleration of hormone release.

Adenylate Cyclase Toxin↗

PubMed1985

Effect of subcutaneous and intranasal administration of ovine corticotropin-releasing hormone in man: comparison with intravenous administration.

Long term use of ovine corticotropin-releasing hormone (oCRH) requires a convenient route of administration. The effects of 0.3, 3, and 30 micrograms/kg BW synthetic oCRH given as a sc injection and of 10 and 30 micrograms/kg given as an intranasal spray were studied in 10 normal men in the late afternoon. Basal plasma immunoreactive ACTH (IR-ACTH) and IR-cortisol levels were 14 +/- 1.9 pg/ml and 4.3 +/- 0.4 microgram/dl (mean +/- SEM). Peak IR-ACTH levels (mean +/- SEM) were 43 +/- 5.5, 53 +/- 8.1, and 64 +/- 8.9 pg/ml after the 0.3, 3, and 30 micrograms/kg doses of oCRH given sc, respectively, and 23 +/- 4.3 and 36 +/- 4.8 pg/ml after the 10 and 30 micrograms/kg doses of oCRH given intranasally, respectively. The lowest sc dose and both intranasal doses caused only single IR-ACTH peaks. After 3 and 30 micrograms/kg sc oCRH, IR-ACTH rose by 15 min, reached an initial peak at 45-60 min, fell rapidly until 90-120 min, and rose to a second peak at 3-5 h. This biphasic response is similar to that previously found after iv administration. IR-ACTH levels remained elevated for 4, 10, and at least 16 h after 0.3, 3, and 30 micrograms/kg sc oCRH, respectively, and for 1.5 and 3 h after 10 and 30 micrograms/kg intranasal oCRH respectively. The effect on IR-cortisol was similar, but more prolonged. Compared to the iv route, sc oCRH produced similar mean peak IR-ACTH and IR-cortisol levels and had a slightly longer duration of action. Intranasal oCRH was only about 1% as effective. Peak plasma IR-oCRH levels in 2 subjects receiving 3 micrograms/kg sc oCRH were 13 and 17 ng/ml at 90 min. These peaks were lower than those after iv administration of the same dose, but the levels remained elevated longer, probably accounting for the longer duration of action of sc oCRH. Peak plasma IR-oCRH levels in 4 subjects given 10 microgram/kg intranasal oCRH were only 64-122 pg/ml, presumably reflecting poor absorption through the nasal mucosa. These results demonstrate that sc injection of oCRH is at least as effective as the iv route with respect to plasma IR-ACTH and IR-cortisol responses. The convenience of this route of administration and the prolonged duration of action of oCRH suggest the feasibility of long term oCRH use.

Administration, Intranasal↗

PubMed1985

Clinical studies with synthetic ovine corticotropin-releasing factor.

Ovine corticotropin-releasing factor (oCRF) stimulates increased plasma immunoreactive adrenocorticotropin (IR-ACTH) and IR-cortisol at threshold, half-maximal, and maximal doses of 0.01-0.03, 0.3-1, and 3-10 micrograms/kg, respectively. Side effects occur with increasing frequency, severity, and duration at doses above 1 microgram/kg. oCRF has a prolonged duration of action, at least in part because of the long circulating half-life of intact oCRF in plasma. Increasing doses of oCRF given in late afternoon progressively diminish the next morning's circadian rise in plasma IR-ACTH in normal subjects, but not in Addisonian patients or subjects receiving metyrapone, indicating that prolonged oCRF-induced hypercortisolemia is the cause. Plasma IR-lipotropins and IR-beta-endorphin rise and fall concomitantly with IR-ACTH after oCRF injection. Arginine vasopressin increases the IR-ACTH response to oCRF fourfold when given simultaneously with oCRF. Cushing's disease patients respond variably, suggesting that oCRF may not be a very useful diagnostic agent in Cushing's syndrome. However, the combination of oCRF with growth hormone-releasing factor, gonadotropin-releasing hormone, and thyrotropin-releasing hormone appears to provide a rapid and useful test of combined anterior pituitary function.

Adrenocorticotropic Hormone↗

PubMed1984

Rapid radioimmunoassay for corticotropin in unextracted human plasma.

This RIA for corticotropin (ACTH) involves use of a commercially available antiserum and permits measurement of immunoreactive ACTH in unextracted plasma. The assay takes 2.5 days, detects as little as 5 pg/mL of plasma, and is specific: structurally and (or) biosynthetically related peptides do not cross react. Generally, data on dilutions of almost all human plasma specimens produce curves parallel to that for the ACTH reference standard. Values correlate well with those obtained by a well-established but more laborious RIA. We measured immunoreactive ACTH in normal subjects at various times of the day and after modulation of their pituitary-adrenal axis, and in patients with hypo- and hyper-secretion of ACTH. We conclude that the full range of immunoreactive ACTH values, which accurately reflect the status of the subject's pituitary-adrenal axis, can be quickly and easily determined in samples of unextracted human plasma.

Adrenocorticotropic Hormone↗