The stimulatory effect of a non-opiate beta-endorphin fragment on arginine-vasopressin release in rats.
The effect of the non-opiate beta-endorphin (beta E) fragment 2-9 and related peptides on immunoreactive (IR) arginine8 -vasopressin (AVP) levels was studied in the rat eye plexus plasma. Additionally, the effect of beta E 2-9 on AVP release from pituitary neurointermediate lobes ( NILs ), in vitro was studied. IR AVP levels in the eye plexus plasma increased after subcutaneous (s.c.) injection of beta E 2-9. In female rats peak values were observed 2 min after the administration of beta E 2-9 (10 micrograms/rat). Male rats were 100 times more sensitive than female rats. A dose-response study revealed a U-shaped relationship for this effect of beta E 2-9 in animals of both sexes. From structure-activity studies it appeared that beta E 2-9 was the most effective fragment. Intracerebroventricular (i.c.v.) administration of beta E 2-9 did not affect the IR-AVP levels in eye plexus plasma. Moreover, AVP release from the rat NILs cells in vitro was stimulated by perfusion with beta E 2-9, indicating a direct effect of the peptide on the pituitary. Therefore we suggest that beta E 2-9 increases AVP release by a direct action on the posterior pituitary.
D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood* / Q000378:metabolism; D004723:Endorphins / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D008297:Male; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D010904:Pituitary Gland, Posterior / Q000187:drug effects* / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013329:Structure-Activity Relationship; D001615:beta-Endorphin
D004723:Endorphins; D010446:Peptide Fragments; D001127:Arginine Vasopressin; D001615:beta-Endorphin; C018903:gamma-endorphin, des-Tyr(1)-; C024770:alpha-endorphin, des-Tyr(1)-; C036560:beta-endorphin (2-9)