| Objective: To investigate the effects of exogenous stem cell factor (SCF) on the gastric electrical activity and gastric impedance in rats with diabetic gastroparesis.Methods: SD rats were randomly divided into experimental group and control group. The rats in experimental group were intraperitoneally injected with streptozotocin (STZ) at dosage of 50mg/kg and irregularly fed with high sugar high fat diet, while normal saline normal diet for control group. Eight weeks later, the rats in experimental group had complication of diabetic gastroparesis which were randomly divided into DGP group (n=8) and DGP+SCF group (n=8). The rats in DGP + SCF group were intraperitoneally injected with exogenous SCF 0.4ug?kg-1?d-1 for 15 days, and the rats in control group and DGP group were intraperitoneally injected with the same amount of phosphate buffer (pH=7.4). The gastric emptying was detected by semisolid residual rate. Gastric electrical activity and gastric impedance were detected by impedance gastric motility acquisition system. The ultrastructure of smooth muscle in the gastric antrum was assessed by transmission electron microscopy. The interstitial cells of cajal were measured by immunohistochemistry and its'microstructure and ultrastructure were observed by transmission electron microscopy. The expressions of mRNA and protein of SCF, the expressions of mRNA and protein of c-Kit in smooth muscle tissue of the gastric antrum were detected by RT-PCR and Western blotting.Results:1. The semisolid residual rate in DGP group was significantly higher than that in control group(60.64%±2.34% vs 43.46%±4.31%, P <0.05); the semisolid residual rate in DGP+SCF group was significantly lower than that in DGP group(52.33%±3.04% vs 60.64%±2.34%, P <0.05).2. There was gastric electrical rhythm disturbance in DGP group, the percentage of dominate frequency of gastric electrical activity was significantly lower than that in the control group (45.36±3.70 vs 55.76±1.94, P<0.01). There was disordered gastric motility in DGP group, the percentage of dominate frequency of gastric impedance was significantly lower than that in the control group (38.08±1.30 vs 51.46±1.44, P<0.01), the percentage of bradygastria frequency of gastric impedance was significantly higher than that in the control group (32.26±0.84 vs 19.57±1.10, P<0.01). The percentage of dominate frequency of gastric electrical activity in DGP + SCF group was significantly higher than that in the DGP group (51.42±1.00 vs 45.36±3.70, P<0.01); the percentage of dominate frequency of gastric impedance was significantly higher than that in the DGP group (39.71±0.89 vs 38.08±1.30, P<0.05), the percentage of bradygastria frequency of gastric impedance was significantly lower than that in the DGP group (31.09±0.81 vs 32.26±0.84, P<0.05).3. The interstitial cells of cajal were located between the circular muscle layer and the longitudinal muscle layer which around the myenteric region. The interstitial cells of cajal in DGP group were significantly fewer than that in control group(0.10±0.01vs 0.32±0.02, P<0.05). The interstitial cells of cajal in DGP+SCF group were significantly higher than that in DGP group(0.18±0.01vs 0.10±0.01, P<0.05).4. The interstitial cells of cajal have slender shape or oval shape. There were abundant of gap junctions between interstitial cells of cajal and smooth muscle cells, between interstitial cells of cajal and neuron cells, between interstitial cells of cajal and themselves. There were abundant of mitochondria, ribosome, endoplasmic reticulum, golgi body in the cytoplasm. In DGP group, the gap junctions between interstitial cells of cajal and smooth muscle cells, between interstitial cells of cajal and neuron cells, between interstitial cells of cajal and themselves were decreased significantly; the organelles in cytoplasm were decreased; vacuoles were formed; mitochondria were swelling and dissolving; endoplasmic reticulum were dilated; part of rough endoplasmic reticulum were degranulation. In DGP+SCF group, the gap junctions between interstitial cells of cajal and smooth muscle cells, between interstitial cells of cajal and neuron cells, between interstitial cells of cajal and themselves were increased significantly; vacuoles were disappeared; mitochondria and endoplasmic reticulum were improved.5. c-Kit mRNA and protein expressed in smooth muscle tissue of the gastric antrum, the content of c-kit mRNA and protein in DGP group were significantly decreased compared with control group (0.485±0.043 vs 1.636±0.113, P<0.05; 0.393±0.031 vs 1.060±0.075, P<0.05); the c-kit mRNA and protein in DGP+SCF group were significantly increased compared with DGP group (1.050±0.081 vs 0.485±0.043, P<0.05; 0.755±0.064 vs 0.393±0.031, P<0.05).6. SCF mRNA and protein expressed in smooth muscle tissue of the gastric antrum, the content of SCF mRNA and protein in DGP group were significantly decreased compared with control group (0.493±0.024 vs 1.787±0.121, P<0.05; 0.546±0.043 vs 1.266±0.080, P<0.05); the SCF mRNA and protein in DGP+SCF group were significantly increased compared with DGP group (0.967±0.087 vs 0.493±0.024, P<0.05; 0.866±0.049 vs 0.546±0.043, P<0.05).7. The smooth muscle cells have spindle shape; the cell nucleus have smooth membrane, less folds and well distributed heterochromatin. The dense patch, dense body, myofilament and a abundant of mitochondria contained in cytoplasm were seen clearly. In DGP group, the nucleus of the smooth muscle cells swell, chromatin margination, sarcoplasmic reticulum and endoplasmic reticulum expansion; the organelles in the cytoplasm dissolved and disappeared in part of smooth muscle cells. In DGP+SCF group, the cell nucleus have slight swelling, dense patch, dense body and myoneme only have a little reduce.Conclusion:1. There was delayed gastric emptying in diabetic gastroparesis rats, exogenous stem cell factor can improve the gastric emptying significantly.2. The interstitial cell of Cajal injured in diabetic gastroparesis rats. Exogenous SCF can make interstitial cells of Cajal increasing and its microstructure and ultrastructure improving. The mechanism would be SCF-Kit signal maintain the phenotype, differentiation and proliferation of the interstitial cells of Cajal.3. The microstructure and ultrastructure of the smooth muscle cells injured in diabetic gastroparesis rats. Exogenous SCF can make its microstructure and ultrastructure improving, but the mechanism is not clear.4. Exogenous SCF can make the injured smooth muscle cells and interstitial cells of Cajal improving; consequently, improve gastric electrical activity and gastric impedance. However, the improvement of gastric electrical activity was more obvious than that of the gastric impedance, but the mechanism is not clear.
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