The effect of tityustoxin in the turnover of inositol phosphates in crude synaptosomes.

The formation of inositol phosphates in response to stimulation by tityustoxin was studied in crude synaptosomes (P2). Phosphoinositides were labelled by incubation in the presence of [3H]inositol. Tityustoxin stimulated the turnover of inositol phosphate (PI). Tityustoxin specifically stimulated the turnover of glycerophosphoinositol (GP1), inositol 1-monophosphate (IP1), inositol 1,4-biphosphate (IP2) and inositol 1,4,5-triphosphate (IP3). The tityustoxin-stimulated turnover of water-soluble inositol phosphates was inhibited by tetrodotoxin, atropine and phorbol myristate acetate. It is suggested that the stimulatory effect of tityustoxin on the turnover of inositol phosphates might be mediated by increases in the release of acetylcholine, caused by the depolarizing effect of tityustoxin.