Biosynthesis of precursor corticotropin/endorphin-, corticotropin-, alpha-melanotropin-, beta-lipotropin-, and beta-endorphin-like material by cultured neonatal rat hypothalamic neurons.

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Enzymatically dispersed hypothalamic cells derived from 15-day-old female rats were maintained in tissue culture for 4 days and then incubated for 2 hr in the presence of [35S]methionine. After such incubation, cell extracts contained multiple forms of 35S-labeled products that were specifically bound by immobilized affinity-purified antisera to corticotropin and beta-endorphin. Sequential use of these immobilized antisera revealed two molecular species (apparent Mr of 33,000 and 36,500) that contained both corticotropin and beta-endorphin antigenic determinants within the same molecule. Substances containing only one of these determinants were also present and co-eluted with corticotropin, alpha-melanotropin, beta-lipotropin, or beta-endorphin upon Sephadex G-50 gel filtration. Extracts of similarly labeled rat anterior and intermediate pituitary lobe cells contained two forms of the common precursor molecule corresponding to the same molecular weights estimated for the hypothalamic material and similar to it with respect to other physicochemical parameters. These data suggest that rat hypothalamus synthesizes corticotropin-related and beta-endorphin-related products via sequential cleavage of a larger common precursor molecule in a manner similar to the processing pathway demonstrated for the intermediate lobe of the pituitary.

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