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

In order to elucidate the presence of free FSH-beta and LH-beta and their relation to the native hormones, immunoreactive FSH (IR-FSH), IR-LH, IR-FSH-beta, and IR-LH-beta subunits in the rat anterior pituitary and serum from 1200hr of proestrous day to 0600hr 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. On the other hand, 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 three different regions. The first peak appeared near the void volume, the second corresponded to that of FSH, and the third was in the region of smaller molecules which was thought to be free FSH-beta. The first and the third peaks ofI R-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 three major peaks corresponding to those of IR-FSH-beta in the extracts. The first peak seemed to be aggregated or non-specifically bound FSH-beta and the second seemed to be FSH, while the third was thought to be free FSH-beta. These results indicated the presence of free FSH-beta in the rat anterior pituitary and serum, and raise a doubt about free LH-beta.