Human beta-endorphin-like immunoactivity was measured in highly trained athletes (n = 10), alcoholics in the early phase of abstinence (n=9) and normal controls (n=15) using the Nichols Allegro immunoradiometric assay. The assay was examined for cross reactivity against related peptides, beta-lipotropin and human N-acetyl beta-endorphin. Venous blood sampling was carried out in the morning at 0900 and 1100 hours in a fasting state. Using two-way analysis of variance there was a significant effect of subject group on beta-endorphin concentration (p=0.029). Post-hoc analysis using the Bonferroni t-test showed that the source of the difference was the alcoholic group having significantly lower beta-endorphin immunoreactivity (p < 0.05). There was no difference between the controls and the athletes. There was a positive correlation between plasma beta-endorphin level at 1100 hours and the subsequent ACTH incremental response to naloxone in the group as a whole (r=0.48, p=0.004). The assay showed 100% cross reactivity with beta-lipotropin and 73% cross reactivity with N-acetyl-beta-endorphin. We conclude that alcoholics have reduced levels of beta-endorphin-like immunoactivity. While beta-endorphin is known not to cross the blood-brain barrier, levels of plasma beta-endorphin-like immunoactivity may indirectly reflect central opioid activity.

We have previously described the effect of ovine CRF on the release of ACTH, Cortisol and aldosterone in sheep (Donald, Redekopp, Cameron, Nicholls, Bolton, Livesey, Espiner, Rivier and Vale 1983). However the response is considerably less than that observed following other stressful stimuli such as haemorrhage (Cameron, Espiner, Nicholls, Donald and MacFarlane 1984). The simultaneous administration of arginine vasopressin (AVP) has been shown to potentiate the action of ovine CRF in vitro (Gillies, Linton and Lowry 1982) and in vivo in the rat (Rivier and Vale 1983). As there is a difference in the structure of rat or human CRF and ovine CRF (Spiess, Rivier and Vale 1983), species specificity in the biological activity of CRF is possible. We have therefore examined the effect of AVP on the ACTH, Cortisol and aldosterone response to ovine CRF in the sheep. Materials and MethodsSix healthy Coopworth wethers weighing between 30 and 50 kg were housed in metabolic cages for at least 5 days before the experiments. Indwelling IV jugular cannulae were inserted at least 18 hours before each study. The animals were fasted but allowed free access to water. The conscious, unrestrained sheep each received a 250 ug IV dose of the synthetic methionine enkephalin analogue DAMME (FK 33-824), a gift from Sandoz Ltd (Basle, Switzerland) an hour before intravenous administration of CRF and/or AVP to block spontaneous ACTH release (Redekopp, Livesey and Donald 1984). Immediately before injection synthetic ovine CRF (Bachem Inc., Torrence, CA, USA) and/or synthetic AVP (Ferring AG, Malmo, Sweden) were dissolved in 0.003 N HC1 and buffered to physiological pH with sheep plasma. Responses were analysed as the increment in area (plasma hormone concentration x time) from the time of AVP and/or CRF administration. Mean incremental areas were compared using Students paired t-test.Plasma hormone concentrations were measured using the following radioimmunoassay procedures; ACTH (Donald 1977), Cortisol (Ruder, Guy and Lipsett 1972), aldosterone (Lun, Espiner, Nicholls and Yandle 1983). The intra-assay coefficients of variation for hormone concentrations resulting in 50% displacement of labelled hormone from antibody were as follows: ACTH 7.5%, Cortisol 5.8%, aldosterone 5.6%. The corresponding interassay coefficients of variation were 14.6%, 6.0% and 15%, respectively.

No abstract

Payne, S.G., J.L. KOltyo: Inhibition of theophylline of the stimulatory effeets of growth hormone on amino acid transport and protein synthesis in musc1e. Endoerinology 87: 1186-1191 (1970) Rillemtl, J.A., J.L. KOltyo: Studies on the delayed action of growth hormone on the metabolism of rat diaphragrn. Endocrinology 88: 240-248 (1971) Rillelflll, J.A., J.L. KOltyo, L.P. Gimpel: Inhibition of metabolie effeets of growth hormone by various inhibitors of eyelie nuc1eotide phosphodiesterase. Bioehim. Biophys. SummaryGrowth hormone (GH) was measured by radioimmunoassay in the urine of diabeties admitted to hospital with ketoacidosis. On the first day of treatment the median immunoreactive growth hormone (IRGH) excretion rate was 3800 nglhr (range 520-40,000 nglhr, n = 6), on the second day, 2450 nglhr (300-9700 nglhr, n = 6), on the third day, 100 ng/hr (4-6700 nglhr, n = 5), and on the fourth day, 80 nglhr (5-4900 nglhr, n = 5). Three to eight months after treatment for ketosis, the GH exeretion rates of 3 of the patients were 0.6, 1.8 and 1.9 nglhr. In nine normals the excretion rate ranged from undetectable to 1 nglhr. The high eoncentration of urinary lRGH in the ketotic patients made possible eomparison of its immunologieal and physical properties with those of extracted pituitary GH (epGH). Immunologieal similarity was indicated by parallelism of dilutions of urinary lRGH and epGH and similar poteney estimates using two different antisera. No signifieant difference in molecular weight or electrical charge could be detected by polyacrylamide gel electrophoresis at pH 4 or 9, and by gel filtration. lt is conc1uded that in ketoacidosis greatly elevated quantities of a GH-like material are exereted in the urine and it is suggested that this may be due to tubular dysfunction. This GH-like material is similar or identical to pituitary GH and hence it may be eonc1uded that at least a portion of plasma GH is also similar to pituitary and urinary GH.

It has been suggested that atrial natriuretic peptide (ANP) is the long-sought inhibitor of corticotropin (ACTH) secretion, but the evidence is conflicting. We have examined the effect of ANP and C-type natriuretic peptide (CNP) on the secretion of ACTH by perifused equine pituitary cells in an in vitro milieu intended to mimic the in vivo milieu in the horse. Corticotropin-releasing hormone (20 pM) and cortisol (0 or 100 nM) were perifused continuously and 7 pulses of arginine vasopressin (AVP; 10 nM) applied for 5 min at 30-min intervals. ANP (1 nM) or CNP (1 nM) were perifused continuously for 75 min, beginning before the 3rd AVP pulse. Neither ANP nor CNP, with or without cortisol, significantly altered the ACTH secretory response to the AVP pulses. We conclude that these natriuretic peptides are unlikely to act at the pituitary as rapid inhibitors of ACTH secretion in the horse.