Release of beta-lipotropin- and beta-endorphin-like material induced by angiotensin in the conscious rat.
1 The influence of the renin-angiotensin system on plasma beta-endorphin-like immunoreactivity (beta-EI) was investigated in the conscious rat by use of a radioimmunoassay for beta-endorphin without prior extraction.2 Intravenous infusion of angiotensin I, II or (des-1-Asp)angiotensin II (angiotensin III) caused a dose-dependent increase in plasma beta-EI, angiotensin III infusion being less effective than angiotensin I or II. The plasma adrenocorticotrophin (ACTH) levels too were elevated by angiotensin II. The receptor antagonist, saralasin, prevented the angiotensin II-induced beta-EI release as did dexamethasone pretreatment.3 Both the release of beta-EI and the pressor response to angiotensin I were abolished by the converting enzyme inhibitor, captopril (SQ 14225). In contrast, captopril did not affect the action of angiotensin II.4 In view of the appreciable cross-reactivity of beta-lipotropin (beta-LPH) in our assay, plasma beta-EI was analysed by Sephadex G-50 chromatography. In plasma extracts of angiotensin II-infused rats, immunoreactivity corresponding to human beta-endorphin comprised about 49% of the total immunoreactivity, whereas 51% co-migrated with human beta-LPH.5 The increase in plasma levels of beta-EI elicited by angiotensin II was diminished by about 35% in rats with a hereditary absolute lack of vasopressin (Brattleboro rats), when compared to normal rats.6 These results suggest that the renin-angiotensin system can stimulate the secretion of beta-LPH and beta-endorphin with ACTH from rat anterior pituitary. One link in mediating the response appears to be vasopressin. The physiological function remains to be defined.
D000803:Angiotensin I / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000805:Angiotensin III / Q000494:pharmacology; D000818:Animals; D002216:Captopril / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004347:Drug Interactions; D004723:Endorphins / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012504:Saralasin / Q000494:pharmacology; D013045:Species Specificity; D001615:beta-Endorphin; D008083:beta-Lipotropin / Q000378:metabolism*
D004723:Endorphins; D000804:Angiotensin II; D000805:Angiotensin III; D001615:beta-Endorphin; D003907:Dexamethasone; D008083:beta-Lipotropin; D000803:Angiotensin I; D002216:Captopril; D012504:Saralasin