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Radioimmunoassays utilizing antisera specific for the carboxyl-terminal portion of human chorionic gonadotrophin (hCG) beta-subunit were used to measure the concentration in human pituitary extracts of an immunoactive hCG factor (hCG') which was different from human LH (hLH). The content of hCG' from different human pituitary pools collected between 1966 and 1979 was relatively constant at 0.5-1.1 microgram per gland. The hCG' concentrations observed in acetone-dried powder of individual human pituitary glands (0.4-26 ng/mg) were close to those reported for full-term placental powder. After separation and partial purification of human pituitary glycoprotein hormones, pituitary hCG' was found mainly in the crude human FSH (hFSH) fraction. It was separated from hFSH by diethylaminoethyl-cellulose chromatography at pH 7 and by gel filtration on Sephadex G-100. On gel filtration its molecular size was larger than that of hLH or hFSH and it was strongly bound to Concanavalin A-Sepharose. The most active preparations of pituitary hCG' obtained by these procedures were approximately 5 per cent as potent by specific radioimmunoassay as hCG purified from pregnancy urine. Although the hCG' content in individual pituitary glands was more variable than the hLH content, on average pituitary hCG' was estimated to be around 25- to 50-fold less than the content of hLH, hFSH or human TSH in the human pituitary gland.

Highly purified human pituitary FSH was partially dissociated by treatment with 8M-urea, and alpha- and beta-subunits were isolated by ion-exchange chromatography and gel filtration. Tests of biological activity by in-vivo assays and in-vitro radioreceptor assays were in good agreement and showed that preparations of isolated alpha-subunit had less than 1%, and beta-subunit from 2 to 10% of the FSH activity of the intact hormone. In contrast to results reported elsewhere, most of the subunit preparations reassociated with counterpart subunit to regain biological activity equal to that of intact FSH (around 160 mg NIH-FSH-S1/mg). The intact FSH recovered as a by-product after isolation of subunits was of high biological activity, and its LH contamination was reduced by more than 90% when compared with thepurified FSH starting material. The subunits are relatively inactive in a radioimmunoassay specific for intact FSH. Sialic acid and tryptophan determinations indicated that both subunits contain sialic acid and that tryptophan is present only in the beta-subunit.