Regulation of Protein Kinase in KCl-induced Contraction of Cat Gastric Smooth Muscle

Kim, Myung Suk; Jo, Yang Hyeok; Yoon, Shin Hee; Hahn, Sang June; Sim, Sang Soo; Shim, Hye Sun; Rhie, Duck Joo; Kim, Seung Rock

Abstract

BACKGROUND AND AIMS: Smooth muscle contraction and relaxation are suggested to be modulated by intracellular Ca2+, protein kinases and tyrosine kinases. To investigate whether protein kinases are invelved in the gastric smooth muscle contraction induced by KCl, the effects of protein kinase inhibitors and tyrosine kinase inhibitors on the contractions were observed in cat gastric muscle.
METHODS
Circular muscle strips were obtained from the fundus of stomach. The isometric contraction of the muscle strips were measured in isolated organ baths using force transducers and polygraph.
RESULTS
KCI caused a dose-dependent contraction of cat gastric smooth muscle, which was dependent on the extracellular Ca2+ concentration and the Ca2+ influx through voltage-dependent Ca2+ channel. Both protein kinase C and tyrosine kinase inhibitors significantly inhibited the KC1-induced contraction. The combined inhibitory effect of two protein kinase inhibitors was greater than that of each one. The combined effects of protein kinase inhibitors together with verapamil were greater than that of each one. Calmodulin antagonists have no inhibitory effect on KCI-induced contraction.
CONCLUSIONS
Protein kinase C and tyrosine kinase are suggested to be involved in the contraction induced by KCl and these protein kinases play a role in the modulation of voltage-dependent Ca2+ channel activity and Ca2+ sensitivity of contractile protein of the cat gastric smooth muscle.