Release of beta-endorphin from rat pituitary in vitro.

The rate of release of beta-endorphin immunoreactivity from the anterior lobe of the rat pituitary in vitro increased in respone to potassium-induced depolarization in a calcium-dependent manner. Potassium-induced depolarization did not, however, change the rate of release from intermediate/posterior lobe. These findings provide support for the view that beta-endorphin may have a humoral function and suggest that beta-endorphin stores in discrete pituitary areas are regulated by different release mechanisms.