On the presence of FSH-.BETA. subunit in the rat anterior pituitary and serum.

Abstract

To elucidate the presence of free FSH[follicle stimulating hormone, follitropin]-.beta. and LH[lutropin]-.beta. and their relation to native hormones, immunoreactive FSH (IR-FSH), IR-LH, IR-FSH-.beta. and IR-LH-.beta. subunits in the rat anterior pituitary and serum from 1200 h of proestrous day to 0600 h of estrous day were measured by radioimmunoassay. The amounts of IR-FSH-.beta. found were always more than those explained by the cross-reaction between FSH, and IR-FSH and IR-FSH-.beta.. IR-LH-.beta. was always less than the amount explained by the cross-reaction with LH, and changes in IR-LH and IR-LH-.beta. were parallel. There was also a difference between IR-FSH and IR-FSH-.beta. gel-filtration patterns in the rat anterior pituitary extracts. IR-FSH was eluted as a single peak, while IR-FSH-.beta. was found in 3 different regions. The 1st peak appeared near the void volume, the 2nd corresponded to that of FSH, and the 3rd was in the region of smaller molecules which was thought to be free FSH-.beta.. The 1st and the 3rd peaks of IR-FSH-.beta. changed characteristically during the estrous cycle. Radioiodinated FSH-.beta., when incubated with the anterior pituitary extracts and applied to gel-filtration on Sephadex G-100, appeared also in 3 major peaks corresponding to those of IR-FSH-.beta. in the extracts. The 1st peak seemed to be aggregated or non-specifically bound FSH-.beta. and the 2nd seemed to be FSH, while the 3rd was thought to be free FSH-.beta.. These results apparently indicated the presence of free FSH-.beta. in the rat anterior pituitary and serum, and raise a doubt about free LH-.beta.