Effect of prostaglandins, inositol 1,4,5-trisphosphate, and phorbol esters on radiation-induced decreases in calcium influx in rat brain synaptosomes

Gamma irradiation $({}^{60}{\rm Co})$ reduced KCl-stimulated voltage-dependent uptake of45 Ca2+ in rat whole-brain synaptosomes. Prostaglandins, inositol 1,4,5-trisphosphate, and phorbol esters were tested for their ability to inhibit radiation-induced decreases in calcium influx. None of the compounds tested alone completely prevented radiation-induced decreases in calcium uptake, but some drug combinations did inhibit decreases. Results suggest that radiation-induced decreases in calcium uptake are due to impairment of protein kinase C activity and mobilization of calcium by these drugs.