Comparison of rat anterior and intermediate pituitary in tissue culture: corticotropin (ACTH) and beta-endorphin.

The forms of immunoreactive beta-endorphin-sized material in extracts of anterior and intermediate-posterior pituitary from the rat examined by the ion exchange chromatography method of Zakarian & Smyth. The anterior pituitary primarily contained material that co-migrated with synthetic camel beta-endorphin(1-31), whereas the intermediate-posterior pituitary contained relatively little such material. The majority of immunoactive beta-endorphin-sized peptides in the intermediate pituitary eluted at lower concentrations of NaCl than did camel beta-endorphin. Conditions were developed for the stable, long-term tissue culture of dissociated intermediate-posterior pituitary cells. Extracts of cells maintained in tissue culture for 18 h or nine days had the same content of immunoreactive beta-endorphin, 16k fragment, ACTH(18-39) (or CLIP) and ACTH(17-24). Throughout the nine days in culture, characteristic cells that could be immunostained with antibodies to various regions of pro-ACTH/endorphin were present; during the time in culture, non-reactive background cells multiplied rapidly. The major proteolytic processing of pro-ACTH/endorphin remained characteristic of intermediate pituitary tissue throughout the nine days in tissue culture, and did not become similar to the simpler pattern of proteolytic processing found in the anterior pituitary.