Release of beta-lipotropin and beta-endorphin from rat hypothalami in vitro

Hypothalamic tissue extracts of rats were chromatographed and beta-endorphin immunoreactivity (beta-Endi) was measured. The two major peaks of beta-Endi co-eluted with beta-lipotropin (beta-LPH) and beta-End respectively. Hypophysectomy caused a local decrease of beta-LPH and beta-End concentrations in the mediobasal hypothalamus. During superfusion of hypothalamic tissue blocks in vitro, membrane depolarization by electric stimulation or 45 mM k+ induced a Ca2+-dependent release of both beta-LPH and beta-End.