Glucose-induced insulin release during acute and chronic hypoxia

Glucose-induced insulin release was studied in young dogs during acute and chronic hypoxia, alone and in combination. Six experimental animals were rendered chronically hypoxic (PaO₂, 43.4 ± 0.5 torr) by creation of a right-to-left shunt at age 6-8 wk. Six control animals underwent sham procedures (PaO₂, 85 ± 2.2 torr) at the same age. During air breathing, glucose-induced plasma insulin increases were similar in chronically hypoxic and control animals. When severe hypoxia was acutely produced by ventilation with low-oxygen mixtures in experimental (PaO₂, 23.7 ± 1.7 torr) and control animals (PaO₂, 26.3 ± 1.0 torr), plasma insulin responses were markedly inhibited in both. On the other hand, acutely lowering oxygen tensions of control animals (PaO₂, 37.5 ± 1.4 torr) to levels close to those of air-breathing chronically hypoxic animals did not affect the insulin responses. These observations suggest that glucose-induced insulin release is inhibited by acute severe hypoxia despite previous chronic oxygen deficiency. In contrast, moderate hypoxia, acute or chronic, does not appear to affect the insulin response to a glucose load.