Open AccessRates of production and consumption of phosphatidic acid upon thrombin stimulation of human platelets
Author(s) -
TYSNES OleBjørn,
VERHOEVEN Adrie J. M.,
HOLMSEN Holm
Publication year - 1988
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1988.tb14064.x
Subject(s) - phosphatidic acid , phosphatidylinositol , inositol , diacylglycerol kinase , stimulation , platelet , thrombin , biochemistry , chemistry , inositol phosphate , pi , phosphate , phospholipid , biology , endocrinology , enzyme , membrane , signal transduction , immunology , receptor , protein kinase c
Human platelets were labelled with [ 32 P]P i and [ 3 H]glycerol before gel filtration. In unstimulated cells, the specific 32 P radioactivity in phosphatidic acid (PtdOH) was similar to that of phosphatidylinositol (PtdIns) but only 4% of that of the γ‐phosphate of ATP. Upon 3 min of stimulation with 0.5 U/ml of thrombin, there was a 20‐fold increase in specific 32 P radioactivity of PtdOH which approached that of the ATP γ‐phosphate. Based on constant rates of synthesis and removal, this thrombin‐induced increase in specific 32 P radioactivity in PtdOH allowed us to calculate the flux of phosphate through PtdOH upon stimulation. Synthesis and removal occurred at rates of 107 and 52 nmol min −1 /10 11 cells, respectively. The specific [ 3 H]glycerol radioactivity was similar in PtdIns, phosphatidylinositol 4‐phosphate and phosphatidylinositol 4,5‐bisphosphate in unstimulated platelets. In PtdOH, it was 50% of that of the inositol phospholipids. Thrombin stimulation induced no changes in the specific 3 H radioactivity of the inositol phospholipids whereas specific [ 3 H]PtdOH increased to the level of these lipids. It is concluded that PtdIns, PtdIns P and PtdIns P 2 exist in a metabolic homogenous pool in human platelets.