Blood glucose and plasma insulin levels during oral glucose tolerance test (2g/kg) were observed every 30 minutes for two hours after the administration of glucose to rabbits who had received prednisolone (2.5mg/kg daily). These levels were also observed in untreated rabbits after the simultaneous intravenous administration of plasma from rabbits pretreated with prednisolone (2.5mg/kg) for three days and plasma to which prednisolone was added in vitro. (1) Blood glucose and plasma insulin was elevated in response to administered glucose. Following three days of treatment with prednisolone glucose tolerance markedly deteriorated but the plasma insulin response was significantly augmented (p<0.01-0.05 in two of four points). (2) Following 21 days of treatment the plasma insulin response to glucose did not show any significant difference from that found on the day prior to treatment, while the glucose tolerance deteriorated to the same degree as that found following three days of treatment. (3) The plasma insulin response to glucose was significantly augmented by simultaneous administration of ten ml of plasma from prednisolone-treated rabbits (p<0.01-0.05). The blood glucose response was not affected by plasma administration. (4) The augmentation in plasma insulin response to glucose was not observed after simultaneous administration of ten ml of untreated-rabbit plasma to which prednisolone (10 and 30μg) was added in vitro. Thus the present study indicated that the prednisolone-administration augmented the plasma insulin response to glucose and that insulin-release-promoting factor could be demonstrated in plasma from these rabbits.

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