| Objective:To investigate the down-regulation of PLC? activity in diabetes rat model and its mechanism in gastric smooth muscle.To elucidate the PLC?-IP3 signaling pathway by which CNP activates PKG and PKA through cGMP and cAMP,and the important role of this pathway in the development of diabetic gastric motility disorders.Methods:The experimental animals were Wistar rats(weight 180-220 g).Diabetes model was established by a single injection of STZ(65 mg/kg)in the abdominal cavity.The effect of CNP on spontaneous contraction of gastric antral smooth muscle was detected by in vitro muscle strip test;Immunohistochemistry and Western blotting were used to detect the changes of PLC?3 and PLC?1 protein levels in normal control group and diabetic group.The changes of IP3 content in normal control group and diabetic group and the effects of CNP?KT5823 and H-89 on IP3 content were determined by ELISA.Results:1.Compared with the normal control group,the expression levels of PLC?3 and PLC?1 in the gastric antral smooth muscle of diabetic rats were significantly decreased(n=9,P<0.05).2.Compared with the normal control group,the phosphorylation of PLC?3S1105 was significantly increased in the gastric antral smooth muscle tissue of diabetic rats,and the activity of PLC?3 was significantly decreased(n=9,P<0.05).3.CNP inhibited the spontaneous contraction of gastric antral smooth muscle in rats in normal group and diabetic group,and compared with the degree of inhibition of contraction amplitude,degree of inhibition of contraction frequency,time of complete inhibition of contraction,and basic tension,CNP for diabetes The inhibition of the group was significantly greater than that of the normal control group(n=8,P<0.05).4.In the gastric antral smooth muscle tissue of diabetic rats,the IP3 content was significantly lower than that of the normal control group(n=8,P<0.05).Adding CNP could significantly reduce the IP3 content in rat gastric antral smooth muscle tissue.It was more pronounced in the diabetic group(n=8,P<0.01).5.In the gastric antral smooth muscle tissue of diabetic rats,PKG and PKA were blocked at the same time,and the effect of CNP on IP3 content was almost offset(n=8,P<0.05)6.In the gastric rat sinus smooth muscle,CNP can promote the phosphorylation of PLC?3S1105(n=9,P<0.05),thereby inhibiting the activity of PLC?3,while inhibiting PKA and PKG can block the phosphorylation of PLC?3S1105 by CNP(n=9,P<0.05).Conclusion:In the gastric antral smooth muscle tissue of diabetic rats,CNP can promote the phosphorylation of PLC?3S1105 through PKG and PKA pathway,reduce the activity of PLC?3,and further reduce the formation of IP3 in gastric smooth muscle cells,thereby inhibiting the spontaneous contraction of gastric antral smooth muscle. |
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