A B S T R A C T Isolated rat islets of Langerhans were incubated for 60, 120, and 180 min and the incorporation of leucine-'H into proinsulin and insulin moieties was followed. Synthesis and release of these hormones could be followed by separate extractions of islets and incubation media.Release
It has been reported that insulin secretion decreases during hypoxia both in vitro and in vitro, while an increase in glucagon secretion is found only in vivo. The effect of acute hypoxia on the secretion of glucagon and insulin was studied in the perfused rat pancreas. Phentolamine, an alpha-adrenergic blocker, was perfused during the period of hypoxia to elucidate the role of alpha-adrenergic stimulation. Sodium ATP and dibutyryl cAMP were also administered to study their effects on insulin and glucagon responses during hypoxia. In the present experiments, insulin secretion was suppressed while glucagon secretion was increased during hypoxia. Phentolamine did not cause any change in insulin of glucagon secretion. When dibutyryl cAMP was added, the increased glucagon secretion was reduced to the basal level, whereas the decreases in insulin secretion were not altered. The addition of sodium ATP reversed the hypoxia-induced decrease in insulin and the increase in glucagon secretion. These results suggest that a decrease in ATP production, which leads to impaired cAMP generation, pays a role in, and that alpha-adrenergic stimulation does not participate in the changes in, insulin and glucagon secretion during hypoxia in vitro.
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