Continuous administration of human corticotropin-releasing hormone in the absence of glucocorticoid feedback in man

Continuous 24-hour infusions of a maximally stimulating dose (1 microgram/kg/h) of corticotropin-releasing hormone (CRH) have been shown to cause elevations of plasma cortisol and ACTH, but the pattern of results were confounded by serum cortisol causing feedback changes. We have looked at ACTH responses to saline or CRH infusions over 24 h in 6 normal subjects who, in addition, received either placebo or metyrapone, an 11 beta-hydroxylase inhibitor which blocks the formation of cortisol and thus abolishes glucocorticoid feedback. Cortisol and ACTH levels were measured by radioimmunoassay. Before metyrapone, CRH infusion resulted in exaggerated ACTH peaks throughout the day, as compared with normal saline: there was no influence on the noctural rise in ACTH. Following metyrapone alone, absolute cortisol levels were lower but circadian rhythmicity was preserved. Circadian rhythm of ACTH was maintained, with a fall in the evening to 14.5 +/- 4 pg/ml (mean +/- SE) at midnight and an exaggerated rise overnight, reaching a peak level of 90 +/- 33 pg/ml at 07:00 h. Subjects receiving CRH with metyrapone showed a similar pattern of responses, but with further enhanced ACTH levels. The evening fall reached a nadir of 30 +/- 6 pg/ml at 01:00 h. With diminished glucocorticoid feedback the nocturnal rise in ACTH was augmented by CRH infusion, with a morning peak of 193 +/- 21 pg/ml at 07:00 h. Thus, continuous infusion of CRH in the absence of steroid feedback leads to a retention of the circadian rhythmicity in ACTH secretion, reset at a higher absolute level.(ABSTRACT TRUNCATED AT 250 WORDS)

Achalasia in central Israel, 1973-83: clinical aspects

In the framework of an epidemiologic study we collected data on all the 162 patients with achalasia in central Israel. The mean (+/- SD) follow-up was 9.9 +/- 8.7 years (range 1-52). At the last, as compared to the initial examination, the clinical condition of the patients had improved: 38% were without dysphagia as compared to 0% initially, 67% did not vomit and 92% did not complain of aspiration as compared to 17% and 68% initially, and 67% did not complain of chest pain as against 36% initially. In contrast, X-ray examinations, endoscopy as well as manometry did not show major changes. Esophageal retention of a semisolid radiolabeled meal 10 min after ingestion was 46 +/- 25% initially and 34 +/- 26% at last examination (NS). Medical therapy was given to 99 patients and a beneficial response was initially noted in 65% of them. About 88.7% had a beneficial response to surgery and 82.7% to pneumatic dilatations which were associated with a 7.3% perforation rate. Overall the clinical course of this unselected, regional group of patients was better than expected.

Endothelin-1 stimulates the in vitro release of neurohypophyseal hormones, but not corticotropin-releasing hormone, via ETA receptors

The endothelins consist of a family of vasoconstrictor peptides originally isolated from endothelial tissue which are now known to be involved in neuroendocrine regulation. However, while there are data indicating the involvement of endothelins in the modulation of the hypothalamo-pituitary-adrenal (HPA) axis, the precise mechanisms involved have been unclear. We have therefore used a previously validated rat hypothalamic explant system in order to investigate the possible modulation of the neurohypophyseal hormones vasopressin and oxytocin, and corticotropin-releasing hormone (CRH), by endothelin-1 (ET-1) and endothelin-3 (ET-3). Following a period of stabilisation, the release of vasopressin, oxytocin and CRH remained approximately constant in successive 20-min incubations. Addition of ET-1 stimulated the release of vasopressin at a dose of 0.1 nmol/l (p < 0.05), and both vasopressin and oxytocin at 10 nmol/l (p < 0.01 and 0.05, respectively). The release of vasopressin and oxytocin induced by 10 nmol/l ET-1 were both totally blocked by co-incubation with either 1 or 10 mumol/l of the specific ETA receptor subtype antagonist cyclo (D-Trp-D-Asp-Pro-D-Val-Leu) (BQ-123). ET-1 had no effect on CRH release in the dose range of 0.1-1,000 nmol/l. In case any possible stimulation of CRH might be masked by simultaneous generation of nitric oxide (NO), an inhibitor of CRH secretion, addition of ET-1 was also carried out in the presence of the NO synthase inhibitor, L-NO-Arg: ET-1 was again without effect in this dose range.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticotropin-releasing hormone: interactions with the immune system

Communication between the neuroendocrine and immune systems is crucial to host defence in both health and disease. Stress adversely interferes with the function of the immune system but the mechanism of such stress-induced immunosuppression is not well understood. Corticotropin-releasing hormone (CRH) is a 41-amino residue peptide which primarily stimulates ACTH secretion. In addition, CRH integrates a series of responses during the stress response. Over the last few years increasing evidence has suggested that CRH, the major stress-integrating peptide, may also directly modulate immune system function. Thus, recent data have demonstrated that CRH acts centrally as an immunosuppressant agent independent of circulating glucocorticoids. This central immunosuppressive effect of CRH is mediated at least partly via the central stimulation of sympathetic outflow. At a peripheral level, the presence of CRH and CRH receptors within cells of the immune system, and its complex effects directly on immune function, suggest that CRH is intimately associated with communication between the neuroendocrine and immune systems.

In vivo and in vitro characterization of the light-regulated cpcB2A2 promoter of Fremyella diplosiphon

When exposed to different spectral qualities of light, many cyanobacteria dramatically alter their phycobilisome rod composition in a process termed complementary chromatic adaptation. In the cyanobacterium Fremyella diplosiphon, this response is associated with differential expression of the cpcB2A2, cpeBA, and cpeCDE operons, which code for the phycobiliproteins phycocyanin and phycoerythrin and the phycoerythrin linker polypeptides, respectively. To define components of the signal transduction pathway involved in light-regulated expression of genes encoding phycobilisome polypeptides, we have used in vivo and in vitro techniques to identify cis-acting sequences and trans-acting factors necessary for the regulation of the red-light-inducible cpcB2A2 operon. Deletion of the cpcB2A2 upstream sequences to -76 bp with respect to the transcription start site had no effect on red-light induction of a cpcB2A2-beta-glucuronidase (GUS) chimeric gene, while deletion to -37 bp abolished GUS expression. Furthermore, a fragment of the cpcB2A2 gene from -76 to +25 bp linked to the untranslated leader of cpcB1A1 (a constitutively expressed operon encoding phycocyanin) is sufficient to drive high-level GUS expression in red light. Therefore, the sequence between positions -76 and -37 is necessary for the expression of cpcB2A2, and the region extending from -76 to +25 is sufficient for red-light induction of the operon. Attempts were made to correlate the in vivo data with protein binding in the region upstream of the transcription start site of cpcB2A2. Using in vitro analysis, we detected two protein-binding sites in the cpcB2A2 promoter which were localized to positions -162 to -122 and -37 to +25. Proteins from both red- and green-light-grown cells interacted with the former site, while only proteins present in extracts from red-light-grown cells interacted with the latter site. The data from both the in vivo and in vitro analyses suggest that while two regions upstream of the cpcB2A2 transcription initiation site specifically bind proteins, only the binding site bordering the transcription start site is important for complementary chromatic adaptation.

An audit of the insulin tolerance test in adult subjects in an acute investigation unit over one year

OBJECTIVE

We audited our practice of insulin tolerance testing (ITT) in terms of safety and technical success. We reviewed the results of those tests performed over a 12-month period. By relating peak cortisol response to 0900 h screening cortisol level, we determined whether we could reduce the number of tests performed.

DESIGN

The results of all ITTs performed on our unit between 1 January and 31 December 1991 were reviewed.

PATIENTS AND MEASUREMENTS

Patients were prescreened by measurement of serum cortisol and thyroxine, and recording of an electrocardiogram. A subnormal serum thyroxine (< 58 nmol/l), 0900 h serum cortisol (< 100 nmol/l) or an abnormal ECG were taken as contraindications to the test. Minimum glucose and maximum cortisol levels were recorded, along with peak GH responses when measured. The peak cortisol response was compared to the screening and basal cortisol levels.

RESULTS

A total of 161 tests were performed, 135 of which fulfilled our inclusion criteria. The test was technically successful in all but 5 of these; a significant adverse event occurred in one patient with full recovery after reversal of hypoglycaemia. Thirty-two patients had a suboptimal serum cortisol response to hypoglycaemia: screening cortisol level ranged from 128 to 493 nmol/l and 0900 h serum cortisol measured prior to the ITT from 97 to 431 nmol/l. The lowest level of screening cortisol above which all patients would be expected to achieve the normal peak cortisol of 580 nmol/l or over is therefore 494 nmol/l. If this cut-off level had been adopted, 10 (8%) ITTs need not have been performed if their only purpose had been to assess cortisol reserve. Altering the criterion for the necessary peak cortisol to 500 nmol/l did not affect the number of ITTs required. Our lower limit for testing could not be revised upwards from 100 nmol/l. Adequacy of cortisol reserve did not predict a normal GH response to insulin-induced hypoglycaemia.

CONCLUSIONS

When performed in an experienced endocrine unit with adequate supervision, the insulin tolerance test is a safe procedure. According to the current sample, fewer tests would be performed without detriment to patient care if those with a screening cortisol of greater than 500 nmol/l did not proceed to testing, unless the purpose of the test was also to exclude GH deficiency. A lower limit of 100 nmol/l appears reasonable and need not be revised upwards.

Interleukin-1 beta and interleukin-6 stimulate neurohypophysial hormone release in vitro

Interleukin-1 (IL-1) and interleukin-6 (IL-6) have been reported to stimulate the release of corticotrophin-releasing hormone (CRH) in vitro, the response being antagonized by the cyclo-oxygenase inhibitor, indomethacin. The effects of cytokines on the other major ACTH-releasing hormone, vasopressin (AVP), and the other neurohypophysial hormone, oxytocin, have been little studied, and the published data are conflicting. We have therefore used a previously validated rat hypothalamic explant model to evaluate whether IL-1 beta and IL-6 can directly activate the AVP and oxytocin neurosecretory system. In addition, we have also investigated the effects of inhibition of cyclo-oxygenase (CO) and lipoxygenase (LO) activities on the stimulated release of AVP and oxytocin by means of a series of antagonists, including a specific LO pathway inhibitor. The static rat hypothalamic incubation system used involves fresh hypothalamic explants with consecutive 20-min incubations, and estimation of AVP and oxytocin concentrations in the medium by specific and sensitive radioimmunoassays. It was found that IL-1 beta produced a dose-dependent increase in the release of AVP and oxytocin at doses of 10 and 100 U/ml (P < 0.005). Only at the higher dose of 100 U/ml was IL-6 able to increase significantly AVP and oxytocin release (P < 0.05). These stimulatory effects of IL-1 beta and IL-6 were blocked by cyclo-oxygenase inhibitors, indomethacin (28 microM) and ibuprofen (100 nM), but not by the lipoxygenase inhibitor, BW A4C (10 micrograms/ml), suggesting that prostaglandins are involved in this process.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of immunoreactive interleukin-1-alpha from rat hypothalamic explants is increased by bacterial lipopolysaccharide and high KCL concentrations

It has previously been shown that interleukin (IL)-1-like bioactivity is released from rat hypothalamic explants in short-term incubations. Experiments conducted with antiserum against IL-1 alpha or IL-1 beta showed that IL-1 alpha is released more abundantly under basal conditions. For the present study, we developed a specific radioimmunoassay to investigate the release of immunoreactive (ir) IL-1 alpha from the rat hypothalamus in short-term experiments, and observed that release of irIL-1 alpha increased with time and was significantly increased by high KCL concentrations. The stimulatory effect of 28 mM KCL was significantly inhibited by verapamil. Subsequent investigation of the effects of putative modulators of IL-1 alpha secretion, bacterial lipopolysaccharide (LPS) and the prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha), showed that irIL-1 alpha release was stimulated by 100 ng/ml LPS, but not by higher concentrations, PGE2 had no effect and PGF2 alpha caused dose-dependent inhibition. However, the latter did not seem to exert a tonic inhibitory influence on irIL-1 alpha release, since blockade of cyclo-oxygenase activity by indomethacin had no effect on cytokine release under basal conditions. We conclude that LPS stimulates and PGF2 alpha inhibits basal release of hypothalamic IL-1 alpha, the characteristics of the secretion of which suggest that it may be, at least in part, of neuronal origin.

Lipopolysaccharide modulation of eicosanoid and corticotrophin-releasing hormone release from rat hypothalamic explants and astrocyte cultures in vitro: evidence for the involvement of prostaglandin E2 but not prostaglandin F2 alpha and lack of effect of nerve growth factor

Bacterial lipopolysaccharide (LPS) and prostaglandins (PG) E2 and F2 alpha are putative activators of the hypothalamo-pituitary-adrenal axis. Certain of the biological effects of LPS may be mediated by cytokines such as interleukin-1 beta (IL-1 beta), while IL-1 beta itself may operate via induction of the prostaglandins and/or nerve growth factor (NGF). As IL-1 beta stimulates the release of corticotrophin-releasing hormone (CRH) from acute rat hypothalamic explants directly, the effects of these substances on the release of CRH in vitro were investigated in short- and medium-term (20 and 60 min) incubations. The effect of LPS on the release of PGE2 and PGF2 alpha from these explants, as well as from cortical astrocyte cultures, was also studied. LPS did not modify the release of CRH, PGE2 or PGF2 alpha in 20-min incubations. In 60-min incubations, LPS stimulated the release of PGE2, whereas the release of CRH was weakly, but significantly, reduced; PGF2 alpha was not altered. PGE2 significantly stimulated CRH release in the 60-min but not in the 20-min experiments. This effect appeared to be selective for PGE2, since PGF2 alpha did not modify CRH release, alone or in combination. LPS also selectively released PGE2 but not PGF2 alpha from cortical astrocyte cultures after 24-h incubation. NGF had no effect on the release of explant CRH, regardless of the length of incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of human corticotropin-releasing hormone to its binding protein in blood may trigger clearance of the complex

Late in the last trimester of human pregnancy, as plasma CRH levels rise, the concentration of circulating CRH-binding protein (CRH-BP) falls. We have investigated, using nonpregnant subjects, the hypothesis that CRH has a negative effect on plasma levels of CRH-BP. A specific RIA developed with the aid of recombinant binding protein has been used to measure CRH-BP. Subjects given iv infusions of human CRH for 10 h showed a sustained fall in plasma CRH-BP for the duration of the infusion. Intravenous bolus injection of human CRH produced a rapid reduction in CRH-BP levels to 54% of the basal value, whereas ovine CRH was without effect, even though both peptides are cleared from the plasma at similar rates and have similar effects on the pituitary-adrenal axis. The rapid clearance was concluded to be related to ligand affinity, as ovine CRH has a 200-fold lower affinity than human CRH for CRH-BP. We suggest that the rising levels of CRH are responsible for the reduction in CRH-BP concentrations observed in late pregnancy, and that this reduction is triggered by the binding of CRH-BP to its ligand.

Functional characterization of the cloned human ACTH receptor: impaired responsiveness of a mutant receptor in familial glucocorticoid deficiency

The putative ACTH receptor gene has been identified on the basis of its tissue specific expression, structure, and limited expression data. We have expressed this gene in COS-7 cells and measured cAMP production in response to ACTH. An EC50 of 5.5 x 10(-9) M for ACTH (1-24) was determined. The S74I mutant ACTH receptor gene that associates with the syndrome of familial glucocorticoid deficiency had an EC50 of 67 x 10(-9) M. This discrepancy is consistent with the clinical data, and supports the hypothesis that this point mutation could account for the syndrome.

A novel receptor tyrosine phosphatase-sigma that is highly expressed in the nervous system

A novel transmembrane receptor protein tyrosine phosphatase-sigma (RPTP-sigma) was cloned from a rat brain stem cDNA library. The extracellular segment of one form of RPTP-sigma contains 824 amino acids and is composed of three immunoglobulin-like and five fibronectin type III (FNIII)-like repeats. The 627-amino acid cytoplasmic region of RPTP-sigma consists of two catalytic domains oriented in tandem. Northern blot analyses indicate that RPTP-sigma is highly expressed in the brain as two major transcripts of 5.7 and 6.9 kilobases (kb). The 5.7-kb transcript is expressed exclusively in the brain while the 6.9-kb species can be detected in the lung and heart, but at significantly lower levels. In situ hybridization studies confirm that RPTP-sigma is localized predominantly in the nervous system and can be detected in the rat as early as embryonic day 12. During embryonic development, RPTP-sigma is expressed extensively in the central and peripheral nervous systems, including the trigeminal and dorsal root ganglia as well as the retina. In adult rat brain, expression is restricted primarily to the olfactory tubercule, cerebellum, and hippocampus. Within the latter structure, RPTP-sigma is present in the pyramidal cell layer and granular layer of the dentate gyrus. Transfection of RPTP-sigma cDNA into human embryonic kidney 293 cells results in the synthesis of a protein with an apparent molecular mass of 200 kDa as detected by immunoprecipitation and immunoblot analyses using polyclonal antibodies against the FNIII-like repeats present in the extracellular domain of RPTP-sigma. The gene for RPTP-sigma has been mapped to distal chromosome 17 in the mouse.

The control of the gonadotrophin releasing hormone pulse generator in relation to opioid and nutritional cues

Human fertility is ultimately dependent upon the regular pulsatile release of gonadotrophin releasing hormone (GnRH) from hypothalamic neurons. The GnRH pulse generator is subject to modulation by a variety of substances, some of which reflect the individual's metabolic status. Endogenous opioids exert a tonic inhibitory effect on GnRH release; this opioid inhibition is dependent upon the gonadal steroid milieu, and may play a role in the initiation of the mid-cycle luteinizing hormone surge. Putative metabolic signals also influence the GnRH pulse generator, and after performing a cross-sectional hormonal and metabolic analysis of amenorrhoeic athletes, we propose that insulin-like growth factor binding protein 1 (IGFBP-1) is such a signal and may play a role in the initiation of puberty.

Epidemiology of achalasia in central Israel. Rarity of esophageal cancer

The epidemiology of achalasia was studied in a predominantly urban, Jewish population of approximately 1.3 million, in central Israel, during the years 1973-1983. One hundred sixty-two proven cases were collected, representing all known patients with achalasia in the study area. There were no gender differences. The majority of cases were diagnosed within two years of onset of symptoms, although the median delay in diagnosis was 4.4 +/- 5.3 years. The disease was rare in the first two decades of life. The prevalence (in 1983) in the first two decades was 0.7/10(5) rising to 36.2/10(5) above age 70. The mean annual incidence in the years 1973-1978 was 0.8/10(5). It rose slightly to a mean annual incidence of 1.1/10(5) in the years 1979-1983. The prevalence of the disease in 1973 and 1983 was 7.9/10(5) and 12.6/10(5), respectively. The age-adjusted prevalence in 1973 was higher in Asian and African born Jews as compared to those born in Europe, America, or Israel. This difference disappeared by the year 1983. No case of cancer of the esophagus was found among our patients. This may be due to the nonselected, regional nature of our series or to the effects of earlier therapy of achalasia in recent decades.

Nitric oxide modulates the release of vasopressin from rat hypothalamic explants

The enzyme nitric oxide (NO) synthase is present in the paraventricular nucleus, while nitric oxide has recently been shown to inhibit the stimulated release of corticotrophin-releasing hormone (CRH) in vitro. Thus the possible role of NO in regulating, vasopressin (AVP), which also plays an important role in pituitary-adrenal activity, has been investigated. The effects were studied of the NO donors, L-arginine, syndnonimine-1 (SIN-1) and sodium nitroprusside, on both the basal and stimulated release of AVP, employing a previously validated system. Rat hypothalami were incubated in either medium alone or medium containing the test substances and hormone release was measured by RIA. The effect of L-arginine in the presence of the NO synthase inhibitor, L-NMMA, was also investigated. L-arginine reduced KCl-evoked AVP release; this effect was reversed by L-NMMA and reduced by the addition of ferrous human Hb. Similarly, SIN-1 and sodium nitroprusside attenuated KCl-evoked AVP release. L-arginine also reduced IL-1 beta-stimulated AVP release. NO appears to directly and specifically inhibit the stimulated release of AVP from rat hypothalamic explants in vitro, similar to its effects on CRH. These findings provide further evidence that NO may be involved in neuroendocrine regulation.

Hyperactivity of the hypothalamo-pituitary-adrenal axis in obesity: a study of ACTH, AVP, beta-lipotrophin and cortisol responses to insulin-induced hypoglycaemia

OBJECTIVE

The purpose of this study was to determine whether alterations in the hypothalamo-pituitary-adrenal axis and arginine vasopressin secretion, which have been associated with animal obesity, also occur in man.

DESIGN

Cross-sectional analysis of extremely obese women and normal weight controls.

PATIENTS

Thirty-three obese premenopausal, non-diabetic women (mean age 31 years, mean body mass index (BMI) 41), and 15 normal weight controls (mean age 24 years, mean BMI 22).

MEASUREMENTS AND RESULTS

Arginine vasopressin (AVP), ACTH, beta-lipotrophin and cortisol responses to insulin-induced hypoglycaemia (0.2 units Actrapid/kg body weight for obese; 0.15 unit/kg for controls) were measured. The obese women were further characterized by anthropometric measurements (weight, body mass index, fat distribution) and indices of insulin secretion/resistance: fasting insulin, insulin secretion during 75-g oral glucose tolerance test area under curve, insulin-stimulated glucose disposal and an index of insulin resistance. No significant differences were found in the basal levels of ACTH, AVP, beta-lipotrophin or cortisol. An augmented peak beta-LPH (n = 16, P < 0.02, the difference of the mean 3.65, 95% confidence interval 1.33-10) and ACTH (n = 16, P = 0.05, the difference of the mean 2.12, 95% CI 1.0-4.5) response were found in obese as compared with normal weight controls. Both ACTH and AVP areas under the curve were similar in both groups studied. There was additionally a direct positive association between the integrated ACTH response (area under the curve) and the weight of the obese subjects (P < 0.05, r2 = 0.265). The cortisol response was negatively correlated with insulin-stimulated glucose disposal (P < 0.01, r2 = 0.23), but not with other indices of insulin secretion/resistance (fasting insulin, oral glucose tolerance test area under the curve, index of insulin resistance) or fat distribution. Comparable responses to hypoglycaemia were seen for AVP and cortisol. There was no correlation between the ACTH, AVP or cortisol responses.

CONCLUSION

Obesity is associated with increased activity of the hypothalamo-pituitary-adrenal axis as supported by augmented ACTH and beta-lipotrophin secretion in response to insulin-induced hypoglycaemia and the positive association between the ACTH response and the body weight of obese women studied.