Phosphoinositide metabolism in resting and thrombin-stimulated human platelets. Evidence against metabolic heterogeneity.
The specific radioactivity of the phosphodiester and phosphomonoester moieties of the phosphoinositides was determined in resting and thrombin-stimulated platelets that were prelabelled with [32P] Pi. In the unstimulated cells, the specific radioactivity of the monoester phosphates of PIP and PIP2 was similar. Both prolonged incubation at 37 degrees C and upon stimulation with 0.5 U/ml of thrombin, the specific radioactivity of the monoester phosphates decreased 10-15% in both polyphosphoinositides. In the unstimulated cells, the specific radioactivity of the diester phosphates was similar in PI, PIP and PIP2 but amounted only to 3% of the activity of the monoester groups. Prolonged incubation of the unstimulated cells as well as stimulation with thrombin induced a similar 5-6 fold increase in specific radioactivity of the diester phosphate of PI, PIP and PIP2. The results indicate that the phosphoinositides in both resting and thrombin-stimulated platelets exist in a metabolically homogeneous pool.
D000255:Adenosine Triphosphate / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology*
D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D000255:Adenosine Triphosphate; D013917:Thrombin