Role of cystosolic calcium, IP3 release in contraction of gastric muscle cells induced by CCK-8 and motilin in rats

Abstract

AIM: It’s not clear: (1) whether CCK-8 and motilin had direct effect on rat isolated gastric smooth muscle cells; (2) whether specific receptors exist on gastric smooth muscle cells; and (3) whether cytosolic calcium and IP₃ were involved during contraction of gastric muscle cells caused by CCK-8 and motilin. The purpose of this study was to investigate the action of CCK-8 and motilin on antrum smooth muscle cells, and role of cytosolic free calcium and IP₃ during contraction of antral muscle cells caused by these peptides.

METHODS: Isolated gastric smooth muscle cells were prepared to observe the contracting effect of CCK-8 and motilin on them. Specific antiserum or receptor antagonists were used to investigate their effects on the action of the peptides; Fura-2AM fluro-labelled method was used to measure intracellular calcium concentration changes after CCK-8 and motilin were added to the gastric smooth muscle cells. Protein competitive binding assay was used to measure IP₃ concentration changes after the above peptides were added.

RESULTS: (1) CCK-8 caused contraction of the antrum smooth muscle cells, the percentage of cell contraction was 10.92% ± 2.26%-19.93% ± 4.30% (P < 0.01), the contraction was dose-dependent between 2.5 × 10^-8-2 × 10^-7 mol/L. CCK-8 antiserum (1:100) and loxiglumide (3 × 10^-8 mol/ L) blocked the effects of CCK-8; (2) Motilin caused contraction of the antrum smooth muscle cells, the percentage of cell contraction was 6.38% ± 1.53%-19.88% ± 1.37% (P < 0.01), the contraction was dose dependent between 10^-11-10^-10 mol/L. Motilin antiserum blocked the effects of motilin; and (3) CCK-8, motilin, increased intracellular Ca²⁺ and IP₃ concentration in gastric antrum circular smooth muscle cells.

CONCLUSIONS: (1) CCK-8, motilin, exert direct effects on gastric smooth muscle cells via specific receptor on cell membrane. (2) Contracting effect of CCK-8 and motilin was induced by Ca²⁺ released from the cytosolic Ca²⁺ storage and [Ca²⁺] increase, which was dependent on IP₃ concentration.

Key Words: Cystosolic calcium, IP₃, CCK-8, Motilin, Rats