title: Evidence for separate serotonin and catecholamine compartments in human platelets.
abstract: Serotonin (5-HT) and the catecholamines (CA), noradrenaline (NA) and adrenaline (Ad), are platelet dense-granule constituents which influence platelet activity and vessel tone. Platelets accumulate 5-HT via an active process whilst CA uptake occurs mainly by passive diffusion. The platelet contents and collagen-stimulated efflux of 5-HT, NA and Ad were examined in normal individuals to establish whether relationships exist between these monoamines. Regression analysis revealed that platelet 5-HT was not related to platelet NA or Ad levels. Platelet NA, however, correlated positively with Ad (r = 0.61, P < 0.01). Collagen-induced release of all three monoamines occurred in a dose-dependent manner. The collagen EC50 values for 5-HT and CA release, however, differed and were greater for 5-HT release: 9.6 +/- 0.8 vs. 3.8 +/- 0.2 microgram/ml collagen, 5-HT vs. NA, P < 0.001; 9.6 +/- 0.8 vs. 3.9 +/- 0.5 microgram/ml, 5-HT vs Ad, P < 0.001. These data may reflect differences regarding the triggering mechanisms for 5-HT and CA release and provide evidence for separate compartments of intra-platelet 5-HT and CA and possibly distinct populations of 5-HT and CA containing dense granules and/or platelets.
authors.affiliation: Department of Medicine, University College London Medical School, Sir Jules Thorn Institute, Middlesex Hospital, UK.
authors.forename: C C
authors.initials: CC
authors.lastname: Smith
mesh_terms: D000328:Adult; D001792:Blood Platelets / Q000737:chemistry* / Q000187:drug effects; D002395:Catecholamines / Q000097:blood* / Q000378:metabolism; D003094:Collagen / Q000494:pharmacology; D004837:Epinephrine / Q000097:blood / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood / Q000378:metabolism; D012044:Regression Analysis; D012701:Serotonin / Q000097:blood* / Q000378:metabolism
chemical_list: D002395:Catecholamines; D012701:Serotonin; D003094:Collagen; D009638:Norepinephrine; D004837:Epinephrine