Vasopressin stimulates release of beta-lipotropin and beta-endorphin in conscious rats as measured by radioimmunoassay of unextracted plasma.
Using a newly developed radioimmunoassay to determine the beta-endorphin-like immunoreactivity (beta-EI) in unextracted plasma, the effect of vasopressin injections on plasma beta-EI was investigated in conscious rats. Arginine vasopressin caused a dose-dependent increase of plasma beta-EI from 34.5 to 7.8 fmol ml--1 (n = 6) in vehicle-treated animals to 205.0 +/- 36.1 fmol ml--1 (n = 7) after injection of the highest vasopressin dose employed (486 ng/100 g b.w.). In view of the appreciable cross-reactivity of beta-lipotropin (beta-LPH) in the radioimmunoassay used, plasma was extracted and subjected to gel chromatography on a Sephadex G-50 column. On average, about 70% of the beta-EI co-eluted with human beta-LPH and about 30% with human beta-endorphin in plasma extracts obtained from both control and vasopressin-treated rats. No peripheral conversion of human beta-LPH occurred under the experimental conditions, since after i.v. bolus injection of human beta-LPH 97% of the beta-EI comigrated with human beta-LPH during gel filtration. A similar blood pressure increase to that induced by the vasopressin injections, when elicited by noradrenaline or angiotensin II i.v., was not followed by an elevation of plasma beta-EI. These data indicate that vasopressin stimulates beta-lipotropin and beta-endorphin release into the systemic circulation in vivo.
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D003429:Cross Reactions; D004723:Endorphins / Q000097:blood / Q000276:immunology / Q000378:metabolism*; D008297:Male; D011863:Radioimmunoassay; D051381:Rats; D014667:Vasopressins / Q000494:pharmacology*; D001615:beta-Endorphin; D008083:beta-Lipotropin / Q000097:blood / Q000276:immunology / Q000378:metabolism*
D004723:Endorphins; D014667:Vasopressins; D001127:Arginine Vasopressin; D001615:beta-Endorphin; D008083:beta-Lipotropin