Abstract: Objective: To investigate the influence of α cells and glucagon-like peptide 1 (GLP-1) in the function of β cells (INS-1 cells) in the rats, and to elucidate the possible mechanism of α cells and INS-1 cells transplantation in influencing hypoglycemia. Methods: The proliferation abilities of INS-1 cells after treated with 10%, 20% and 30% islet α-cell conditioned medium and 0.03, 0.30, 3.00, 30.0 mg · L^-1 of GLP-1 were analyzed by MTT assay. The levels of insulin secretion of INS-1 cells after treated with 10%, 20%, 30% α cells, α-cell conditioned medium and different concentrations of GLP-1 were analyzed by enzyme linked immunosorbent assay (ELISA). The concentrations of Ca²⁺ in INS-1 cells after treated with high glucose and GLP-1 were analyzed by laser confocal microscope. The expression levels of insulin protein after treated with different concentrations of islet α-cell conditioned medium and different concentrations of GLP-1 were detected by Western blotting methed. After the INS-1 cells, the mixture of INS-1 cells and α cells were transplanted into the left renal capsule of the nude mice, the blood glucose levels and the kidney morphology were observed. The levels of insulin/glucagon in the transplanted cells were detected by immunohistochemistry. Results: Compared with control group,both of α-cell conditioned media and GLP-1 promoted the INS-1 cell proliferation and insulin secretion (P<0.05). The laser confocal microscope results revealed that GLP-1 stimulated the increased intracellular Ca²⁺ concentration in INS-1 cells (P<0.05). Compared with control group, there was no significant difference in the expression levels of insulin protein in the insulin-1 cells after treated with islet α cell conditioned medium and GLP-1 (P>0.05). Compared with pre-transplantation, the blood glucose level in the transplanted INS-1 cells was significantly decreased at 35 d after renal capsul trasplantation(P<0.05), and even hypoglycemia presented renal capsular in the diabetic nude mice; the transplantation site was obviously swollen. However, the levels of blood glucose had no change of the diabetic rats after transplated with the mixture of INS-1 and α cells(P<0.05).The expression of insulin and glucagon in the INS-1 transplanted cells were found by immunohistochemistry staining. Conclusion: Pancreatic islet α cells and their secretions can promote the INS-1 cell proliferation and insulin secretion, and the mixture of INS-1 cells and α cells transplanted under the renal capsule of the diabetic nude mice can reduce the hypoglycemic effect of INS-1 cell transplantation which might be related to the INS-1 cells that can express both of insulin and glucagon genes.

Key words: pancreatic islet β cells, glucagon-like peptide 1, insulin, diabetes mellitus, pancreatic islet α cells