A rat hypothalamic extract enhances insulin secretion in vitro.

Fractions from a partially purified ventrolateral hypothalamic (VLH) extract stimulate insulin (IRI) secretion when infused into isolated perfused rat pancreases. At a low glucose concentration (5 mM) in the perfusion medium, infusion of the VLH extract significantly increased insulin output when compared to controls infused with a cerebellar cortex extract. (IRI output with cerebellar cortex: 13.5 +/- 0.81; with VLH extracts: 40.9 +/- 9.4 ng/5 min, P less than 0.05). At a high glucose concentration (10 mM) in the perfusion medium, IRI secretion evoked by glucose was further augmented by the simultaneous infusion of the VLH extract (IRI output with glucose: 325.6 +/- 25.8; glucose + VLH extract: 448.1 +/- 33.0 ng/20 min, P less than 0.02). When pancreases were perfused with a solution containing 20 different amino acids [(AA) 6.6 mM final concentration] IRI secretion elicited by the AA was similarly augmented by the presence of the VLH extract (IRI output with AA: 101.8 +/- 14.9; AA + VLH extract: 179.8 +/- 21.9, P less than 0.02). However, IRI secretion as stimulated by arginine alone (3 mM) was not potentiated by the extract. It is suggested that the hypothalamic factor(s) responsible for this IRI secretion-promoting activity could contribute to the hypothalamic control of IRI secretion through a route which remains to be established.