SOLUBILIZATION AND CHARACTERIZATION OF HIGH-AFFINITY FOLLICLE-STIMULATING-HORMONE RECEPTORS FROM PORCINE GRANULOSA-CELLS

Follicle-stimulating hormone (FSH)-receptors were solubilized from imm ature porcine ovarian granulosa cells with retention of high affinity I-125-porcine FSH-binding activity. The optimal concentration of Trito n X-100 for solubilization was 0.5% (w/v), and the optimal cellular pr otein concentration 25 mg/ml. Glycerol (30%) increased recovery of sol ubilized receptor. I-125-pFSH-binding affinity ranged from 4 x 10(10) M-1 to 8 x 10(10) M-1 in either the absence or presence of glycerol. I -125-pFSH-binding capacity was 5 fmol/mg protein in the absence of gly cerol and 58 fmol/mg protein in the presence of glycerol as determined by equilibrium saturation binding analysis. By gel permeation chromat ography, the apparent size of the I-125-pFSH-receptor complex was 462 kDa in the absence of glycerol and 762 kDa in the presence of glycerol . Ligand blotting of solubilized receptor yielded a single species wit h an apparent molecular weight of 200 kDa under nonreducing conditions and a single species with an apparent molecular weight of 60 kDa unde r reducing conditions. These studies indicated that high affinity FSH- binding activity can be solubilized from membranes of immature porcine granulosa.