Biosynthesis and Secretion of Follicle-Stimulating Hormoneβ-Subunit from Ovine Pituitary Cultures: Effect of 17β-Estradiol Treatment*

An assay was developed to detect tritium-labeled ovine FSH beta-subunit [( 3H]oFSH beta) secreted from primary ovine pituitary cultures. This procedure used affinity-enriched antibodies raised against reduced and carbamylmethylated oFSH beta (RCM-oFSH beta) in a two-cycle immunoextraction procedure. A discrete species with an apparent mol wt of 21,000 was detected in sodium dodecyl sulfate electrophoretic patterns of immunoextracts from culture medium. This species was identified as RCM-[3H]oFSH beta by its comigration with highly purified RCM-oFSH beta, its reduction in culture media after cultures were treated with 17 beta-estradiol, which normally decreases radioimmunoassayable oFSH; and its displacement from the extracting antibodies by excess unlabeled RCM-oFSH beta. The assay was used in a pulse-chase study to determine that [3H]oFSH beta is secreted within 1-2 h of its synthesis. Prior treatment of cultures with 17 beta-estradiol did not change this timing of secretion.