INVOLVEMENT OF PROTEIN-KINASE-C IN CA-2+-INDEPENDENT CONTRACTION OF RAT UTERINE SMOOTH-MUSCLE

The contribution of protein kinase C to the contraction by oxytocin of rat uterine longitudinal smooth muscle in Ca2+-free solution was investigated. Immunological analysis revealed that type II (β) and III (α) protein kinase C subspecies were present in rat uterine smooth muscle. The pretreatment of a diacylglycerol kinase inhibitor R59022 to accumulate diacylglycerol potentiated the Ca2+-independent contraction. The contractile activity was diminished with the depletion of protein kinase C, when the contraction was evoked repeatedly by oxytocin during the prolonged exposure to a tumor-promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate. These results suggested the involvement of protein kinase C in oxytocin-induced contraction in Ca2+-free solution. © 1991.