Properties of PAF-acether-induced platelet aggregation and secretion. Studies in gel-filtered human platelets.
Human platelets rapidly lose their responsiveness to PAF-acether after blood collection. We collected blood from fasting donors and prepared gel-filtered platelets that remained responsive to PAF-acether for about 6 hours. Log-dose response studies showed biphasic aggregation between 20 and 100 nM PAF-acether with secretion of dense-, alpha- and lysosomal granule contents during the second wave of aggregation. Between 0.2 and 10 nM PAF-acether aggregation was weak and no secretion occurred whereas 300 nM PAF-acether or more induced maximal aggregation and secretion. Secretion, however, was never more than 70, 55, and 30% of maximal secretable amount of 5HT, beta TG and beta N, respectively. Aggregation and secretion were enhanced by fibrinogen (optimal concentration 0.3-0.7 g.1(-1)), required Ca2+ or Mg2+ but were inhibited when Mg2+ or Ca2+ were present at a concentration of 2 mM or more. These data show that human platelets are almost equally sensitive to PAF-acether as rabbit platelets, and respond with incomplete secretion of dense-, alpha- and lysosomal granule contents.
D000118:Acetylglucosaminidase / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D002850:Chromatography, Gel; D005340:Fibrinogen / Q000502:physiology; D006801:Humans; D008274:Magnesium / Q000502:physiology; D010972:Platelet Activating Factor / Q000502:physiology*; D010974:Platelet Aggregation; D011817:Rabbits; D012701:Serotonin / Q000378:metabolism; D001620:beta-Thromboglobulin / Q000378:metabolism
D010972:Platelet Activating Factor; D001620:beta-Thromboglobulin; D012701:Serotonin; D005340:Fibrinogen; D000118:Acetylglucosaminidase; D008274:Magnesium; D002118:Calcium