Parallel release of ACTH, β-endorphdm, α-MSH and β-MSH-like immunoreactivities in rat anterior pituitary cells in culture

Abstract

Specific radioimmunoassays (RIAs) for ACTH, β-endorphin, α-MSH and β-MSH were used to identify the immunoreactive components released during incubation of rat anterior pituitary cells in primary culture. Such measurements were performed after separation of the incubation media by chromatography on Sephadex G-50 or G-75. The ACTH-RIA measured approximately equal amounts of 13 and 4.5 K ACTH while equal proportions of components migrating at the position of (β-LPH and β-endorphin were measured in the β-endorphin RIA system. Immunoreactive components migrating at the position of γ-LPH and α-MSH were measured in the β-MSH and α-MSH RIA systems, resp. 3 purified corticotropin-releasing fractions (CRF) prepared from porcine hypothalami and increasing concentrations of N 6, O 2-dibutyryl cyclic AMP and theophylline led to parallel release of ACTH, (β-endorphin, β-MSH and α-MSH immunoreactivities while preincubation with dexamethasone led to a 30–60% inhibition of the release of all peptides. The present data show that the release of ACTH, β-LPH, β-endorphin, γ-LPH and α-MSH-like immunoactivities occurs in parallel in anterior pituitary cells in culture both under basal and acute stimulatory or inhibitory conditions of release.