The role of receptor-operated Ca2+ influx in endothelin-induced contraction of the muscularis mucosae

We examined the role of receptor-operated Ca2+ influx in endothelin-1 (ET-1)- or sarafotoxin S6c (S6c)induced contraction of the muscularis mucosae. Responses of the esophageal muscularis mucosae isolated from guinea-pigs were recorded by an isotonic transducer and a polygraph. ET-1 and S6c produced contraction of the esophageal muscularis mucosae in a concentration-dependent manner. The contractile responses to ETs were abolished in a Ca2+-free EGTA-containing medium, weakly inhibited by nicardipine, and markedly inhibited by SK&F96365, In addition, both H-7 and U-73122 strongly inhibited the ET-induced contractions, but U-73343 weakly inhibited these responses. These results indicate that the esophageal muscularis mucosae of guinea pigs has ET receptors that are coupled mainly to receptor-operated Ca2+ influx and linked with the phospholipase C-protein kinase C pathway.