title: Met5-enkephalin-arg6-phe7 content of human and rabbit plasma.
abstract: Using an adsorption technique combined with high pressure liquid chromatography and a specific radioimmunoassay, the met5-enkephalin-arg6-phe7 (YGGFMRF) content was measured in human and rabbit plasma. This heptapeptide content was 0.16 +/- 0.03, 0.20 +/- 0.05 pmol/10 ml plasma, for human and rabbit plasma, respectively. The degradation of YGGFMRF injected intravenously (rabbit) or that of the opioid heptapeptide added to rabbit plasma is rapid. The biological half life (T 1/2) of 125I-YGGFMRF in rabbit plasma was about 45 seconds (in vivo) and 1 minute and 8 seconds (in vitro). The metabolic clearance rate of YGGFMRF is slower than that of met5-enkephalin. The YGGFMRF content of rabbit plasma increased following inhibition of dipeptidyl peptidase activity by an intravenous injection of captopril. The presence of met5-enkephalin-arg6-phe7 into circulation indicates that it may have some physiological role, however it is unknown whether circulating YGGFMRF originates from adrenal medulla, intermediate lobe of pituitary or some other site.
mesh_terms: D000328:Adult; D000818:Animals; D002216:Captopril / Q000494:pharmacology; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000037:antagonists & inhibitors; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000097:blood; D005260:Female; D006207:Half-Life; D006801:Humans; D008297:Male; D008875:Middle Aged; D011817:Rabbits
chemical_list: D004744:Enkephalin, Methionine; C027511:enkephalin-Met, Arg(6)-Phe(7)-; D002216:Captopril; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases