| Objective:The main purpose of this paper is to investigate the changes in the activity of protein kinase C α protein(PKCα)in the gastric smooth muscle of diabetic rats and its mechanism during diabetic gastric motility disorder,and to state C-type natriuretic peptide(CNP)inhibits the activity of PKC through the protein kinase G(PKG)/protein kinase A(PKA)signaling pathway in gastric smooth muscle tissue,thereby changing the content of Inositol tetraphosphate(IP4)and(Diacylglycerol)DG,and understanding its utility in the occurrence of diabetic complications and gastric motility disorders.Methods:The animals selected for this study were SD rats(male or female,weight 180-220g),and a single intraperitoneal injection of streptozotocin(STZ,65 mg/kg)was used to create a diabetes model;using immunohistochemistry and Western blotting techniques,we observed the distribution of PKCα,PKCβⅠ,PKCβⅡ and their protein-membrane ratios in the smooth muscle tissues of the gastric antrum of rats in the normal control group and the diabetic group,and also observed the changes in the phosphorylation level of PKCα;the isolated muscle strip experimental technique was used to detect the spontaneous contraction of gastric antral smooth muscle with CNP;in the normal control group and the diabetic group,the enzyme-linked immunosorbent assay was used to determine the content of IP4 and DG in the smooth muscles of the gastric antrum of rats,and the influence of CNP,KT5823 and H-89 on the content of IP4 and DG in the smooth muscles of gastric antrum in the two groups of rats were also examined.Results:1.The expression of PKCa protein in the smooth muscle tissue of the antrum of diabetic rats is appreciably less than that in the normal control group(n=9,P<0.05).2.The ratio of PKCα cell membrane to cytoplasm and the ratio of PKCβⅠ cell membrane to cytoplasm in gastric antral smooth muscle tissue of diabetic rats were significantly down-regulated(n=9,P<0.05).3.The phosphorylation level of PKCa in gastric antrum smooth muscle tissue of diabetic rats was obviously lower than that in the normal control group,and the activity of PKCa was down-regulated(n=9,P<0.05).4.CNP has the ability to inhibit the spontaneous contraction of the gastric antral smooth muscle of rats in the normal group and the diabetic group,and the contraction amplitude,contraction frequency,contraction complete time,and basal tension will all decrease.Its ability to inhibit the contraction of gastric antrum smooth muscle in the diabetes group is much greater than that of the normal control group.(n=8,P<0.05).5.The content of IP4 in the smooth muscle tissue of gastric antrum in diabetic rats was significantly down-regulated compared with the normal control group(n=8,P<0.05).CNP has an inhibitory effect on the ability of gastric antrum smooth muscle tissue to produce IP4 and DG,and it is more pronounced in diabetic rats(n=8,P<0.01).6.After blocking PKG and PKA with KT5823 and H-89 at the same time,the function of CNP to reduce IP4 and DG content was basically cancelled in gastric antrum tissue.(n=8,P<0.01).Conclusion:1.PKCa protein is reduced in gastric smooth muscle tissue of diabetic rats,and the activity of PKCa is also down-regulated,inhibiting smooth muscle contraction;2.CNP can reduce the content of IP4 and DG in the gastric smooth muscle tissue of diabetic rats through the PKG/PKA signal pathway,thereby inhibiting the contraction of gastric smooth muscle.These changes may play an important role in the mechanism of diabetic gastroparesis. |
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