Influence of whole-body gamma irradiation upon arachidonic acid metabolism in rat platelets.

The effects of whole-body gamma irradiation (8.4 Gy) were studied on arachidonic acid (AA) metabolism in rats' blood platelets, from day D + 1 to day D + 10 after irradiation. AA conversion into thromboxane B2 (TxB2) increased at D + 1 and then gradually decreased to very low values from D + 7 to D + 10. This decrease in the conversion of exogenous AA into TxB2 was due to a lower AA incorporation into platelets and not to a decrease of cyclooxygenase and thromboxane-synthetase activities. AA incorporation into membrane phospholipids of blood platelets was much more decreased than AA incorporation into whole platelets; moreover, the lipid composition of the platelet membranes was markedly modified after irradiation, which must have resulted in structural and functional changes in these membranes; from these effects of whole-body gamma irradiation on platelets, the latter's membranes appeared as a major site of in vivo radiation damage in these cells.