[Signal transduction pathway for antral smooth muscle cell contraction induced by motilin and gastrin in rats].

Signal transduction pathway that mediates motilin and gastrin induced contraction of antral smooth muscle cells was investigated in rats. The results are as follows. (1) Motilin and gastrin induced contraction of isolated gastric smooth muscle cells in a dose dependent manner. (2) Motilin and gastrin induced antral smooth muscle cell contraction was inhibited by antibodies against G( i-3). Motilin and gastrin caused an increase of Guanosine 5 -(3- (35)S thio)triphosphate( (35)S GTPgammaS) binding of G( i-3). (3) Contraction of antral muscle cells induced by motilin and gastrin was inhibited by the phospholipase C (PLC) inhibitor U 73122 and the IP(3) receptor antagonist heparin. The results suggest that motilin and gastrin induced contraction of rat antral smooth muscle cells is mediated by stimulating G(I) protein coupled with PLC that produces IP(3).