The Hypothalamic Origin of an Insulin Secretion Promoting Factor Present in the Plasma of Normal Rats

Hypothalamic and plasma extracts from normal rats both contain a factor whose property is to stimulate insulin secretion. The two factors have many characteristics in common. Both are active in vivo (when administered to normal recipient rats) and in vitro (when infused into perfused rat pancreases). Both are inactivated by HCI hydrolysis. Both elute at the same ratio between elution volume of the peaks and void volume after gel‐chromatographies are carried out, first on Sephadex G‐50, then on Biogel P‐2, indicating that they have a similar molecular weight which ranges between 800 and 1,200 Daltons. When anaesthetized rats are submitted to an acute bilateral electrical stimulation of the lateral hypothalamus, the insulin secretion stimulating activity present in the plasma is enhanced compared to that measured in sham‐stimulated control rats. Conversely, the insulin secretion promoting activity is decreased in plasma from rats whose ventral hypothalamus is acutely and electrolytically lesioned. These data indicate that, in normal rats, the hypothalamus contains an insulin secretion promoting factor that is releasable in the plasma.