Met-enkephalin immunoreactivity in blood platelets.
Picogram amounts (50-150 pg/mg protein) of immunoreactive met-enkephalin material (met-enkephalin IR) were detected by radioimmunoassay in human, rat and rabbit platelets. Characterization of this material by thin-layer chromatography, gel filtration chromatography and high-pressure liquid chromatography indicated that it behaves identically with synthetic met-enkephalin. No high molecular weight met-enkephalin IR could be detected in the platelet extracts, even after trypsin hydrolysis, using two antisera which are able to recognize some of the putative met-enkephalin precursors present in the adrenal gland or striatum. In vitro, thrombin released platelet-met-enkephalin IR concomitantly with 5-hydroxytryptamine (5-HT), suggesting a common subcellular localization, i.e. the 5-HT storing organelles, for met-enkephalin IR and the amine. In vivo, platelet met-enkephalin IR in the Sprague-Dawley rat was affected neither by adrenalectomy nor by hypophysectomy. Thirteen-and 18-week-old spontaneous hypertensive rats (SHR) had lower platelet concentrations of met-enkephalin IR than age matched normotensive Wistar-Kyoto rats.
D000311:Adrenal Glands / Q000502:physiology; D000818:Animals; D001792:Blood Platelets / Q000032:analysis*; D004723:Endorphins / Q000032:analysis*; D004744:Enkephalin, Methionine; D004745:Enkephalins / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D006801:Humans; D006973:Hypertension / Q000097:blood; D008297:Male; D010902:Pituitary Gland / Q000502:physiology; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology
D004723:Endorphins; D004745:Enkephalins; D012701:Serotonin; D004744:Enkephalin, Methionine; D013917:Thrombin