EFFECT OF P-2-PURINOCEPTOR ANTAGONISTS ON HEMOLYSATE-INDUCED AND ADENOSINE 5'-TRIPHOSPHATE-INDUCED CONTRACTIONS OF DOG BASILAR ARTERY IN-VITRO

OBJECTIVE: To test the hypothesis that the vasoactive effects of hemol ysate of dog erythrocytes on dog basilar artery in vitro are caused by adenosine 5'-triphosphate (ATP). METHODS: Dog erythrocyte hemolysate was assayed for ATP by high-pressure liquid chromatography. Dog basila r arteries were cut into rings and studied under isometric tension to determine the effects of the P-2-purinoceptor antagonists suramin, pyr idoxal phosphate-6-azophenyl-2',4'-disulfonic acid, and reactive blue 2 on contractions induced by hemolysate, prostaglandin F-2 alpha (PGF( 2 alpha)), KCl, uridine 5'-triphosphate, and ATP. RESULTS: Dog erythro cyte hemolysate contained 34 mu mol/L of ATP. Hemolysate produced conc entration-dependent contractions of dog basilar artery. Suramin (100 m u mol/L) significantly inhibited contractions to hemolysate, ATP, and uridine 5'-triphosphate but not to PGF(2 alpha) and KCl (P <0.05). Pyr idoxal phosphate-6-azophenyl-2',4'-disulfonic acid (100 mu mol/L) caus ed a small but significant reduction of the contractions to hemolysate and did not affect contractions to PGF(2 alpha) and KCl. Reactive blu e 2 (30 mu mol/L) produced significant inhibition of contractions to h emolysate and PGF(2 alpha) but did not affect contractions to KCl. CON CLUSION: These findings suggest that ATP mediates a smooth muscle cont ractile response of hemolysate on dog basilar artery. Because erythroc yte cytosol is known to be important in the pathogenesis of vasospasm, these results suggest that ATP may contribute to the vasoconstriction that occurs in vasospasm.