The preferential release of beta-endorphin from the anterior pituitary lobe by Corticotropin Releasing Factor (CRF)

Although a number of investigators have shown that release of ACTH is accompanied by the release of Beta-endorphin ([beta]-End) and Beta-lipotropin ([beta]-LPH), the proportion of the latter two peptides released with stress or by CRF is unclear. To evaluate directly the release of [beta]-End versus [beta]-LPH from the anterior lobe, we used molecular sieving of plasma and subsequent radioimmunoassay to measure release of both [beta]-End and [beta]-LPH into plasma after thirty minutes of inescapable intermittent footshock. We found a substantial increase in circulating [beta]-End which appears to be of anterior lobe origin. The [beta]-End does not appear to represent peripheral conversion of [beta]-LPH to [beta]-End since the ratio of [beta]-LPH:[beta]-End released remained constant between five and thirty minutes of stress, and the rate of disappearance of [beta]-LPH is slower than the rate of disappearance of [beta]-End following the termination of stress. Further confirmation of these findings was obtained by examining the POMC derived peptides released by pituitary cell suspensions in the presence and absence of oCRF. While unstimulated release consisted of equal proportions of [beta]-End and [beta]-LPH, stimulation of the anterior lobe cell suspensions with oCRF resulted in the release of two-fold more [beta]-End than [beta]-LPH.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26129/1/0000205.pd