Insulin Release in Rats 1 and 5 Days after Hypophysectomy

Abstract
The effect of an i.v. glucose (0.5 g/kg body wt) and in i.v. glibenclamide (1 mg/kg body wt) injection on insulin release was studied in conscious rats shortly after hypophysectomy. One and 5 days after removal of the pituitary gland both the fasting blood glucose and the serum insulin concentrations were significantly lower when compared with control rats as was the insulin response to the stimulation by glucose or glibenclamide. To elucidate the contribution of the lower fasting blood glucose to the decreased insulin release, the effect of a continuous glucose infusion (2 ml/h of a 40% glucose solution) was studied in hypophysectomized rats. The artificial hyperglycemia for 4 1/2 days did not alter the low glucose-induced insulin release in these animals. The results clearly show that under appropriate in vivo conditions the diminished .beta.-cell function can be detected very shortly after hypophysectomy. Evidently the depressed insulin release in hypophysectomized rats is not related to the lower blood glucose concentration.
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