LH/hCG receptor in pig follicular fluid

Follicular fluid isolated from large porcine follicles has been shown to have a specific water soluble 125I-hCG binding sites. After the binding of hCG to follicular fluid the receptor was stabilized against thermal denaturation. The release of LH/hCG receptor into follicular fluid was found to be dependent on its level in follicular cells which was increased together with the maturation of the follicle matures and, in part, could be related to membrane fluidity of the cells. The degree of fluorescence polarization of DPH and the order parameter of 5-doxyl-stearic acid labelled granulosa cells were lower in cells harvested from large follicles (6-12 mm) than in cells from small follicles (1-2 mm). It is suggested that soluble LH/hCG receptor may be actively released from follicular cells into follicular fluid. Specific hCG binding sites were found in the follicular fluid of the pig, rabbit, rat and cow, but not in that of sheep.