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Effect of Starvation on the Pancreatic A-cell and B-cell Functions in Rats
Katsumi Fujiyama
First Department of Internal Medicine, Faculty of Medicine, Tottori University, Yonago 683, Japan
There has been no study in ngard to the precise effect of starvation on the pancreatic A-cell and B-cell functions. To elucidate this issue, the secretion of insulin and glucagon in vivo [glucose (0.5 g/kg), arginine (0.5 g/kg), epinephrine (10 µg/kg) and insulin (0.6 U/ kg) infusion test] and in perfused pancreas was investigated in 6 rats starved for 48 h and 6 rats after overnight fast served as controls, respectively. In the glucose infusion test, the increment in insulin and the decrement in glucagon were significantly (P < 0.01 and P < 0.05) lower in 48 h fasted rats (67.3 ± 6.6 µU/mL and 3.5 ± 5.8 pg/mL, mean ± SEM) than in controls (121.7 ± 10.3 µU/mL and 21.0 ± 3.3 pg/mL), respectively, and the increment in blood glucose was significantly (P < 0.05) greater in 48 h fasted rats (235.7 ± 9.9 mg/dL) than in controls (189.8 ± 13.1 mg/dL). In arginine and epinephrine infusion tests, insulin and glucagon responses were not significantly different between 48 h fasted rats and controls. In the insulin infusion test, the increment in glucagon response to hypoglycemia was signifircantly (P < 0.001) Iower in 48 h fasted rats (99.5 ± 10.3 pg/mL) than in controls (243.2 ± 24.0 pg/mL). In perfused pancreas, insulin response to 16.7 mM glucose and glucagon response to 1.7 mM glucose were significantly lower in 48 h fasted rats, while glucagon response to epinephrine (200 pg/ mL) and both insulin and glucagon responses to 20 mM arginine in the presence of 5.6 mM glucose were almost the same in the 2 groups. These results indicate that starvation induces glucose insensitivity of the pancreatic A-cell as well as that of the pancreatic B-cell, which leads to glucose intolerance.
Key words: glucagon; glucose sensitivity; insulin; perfused pancreas; starvation