| Abstract: | The structure of the lutropin/choriogonadotropin (LH/CG) receptor of a clonal strain of cultured Leydig tumor cells (designated MA-10) and primary cultures of porcine granulosa cells was studied by cross-linking 125I-labeled derivatives of human CG and ovine LH with bifunctional succinimidyl esters. We show that in both cell types, both subunits of the receptor-bound hormone become cross-linked to a single cellular component of Mr = 106,000, when analyzed in the absence of reducing agents, and of Mr = 83,000 when analyzed in the presence of reducing agents. We also present a detailed investigation on the effects of several collagenase preparations on the structure and some functions of the LH/CG receptor. Our results show that the LH/CG receptor is exquisitively sensitive to degradation by these preparations of collagenase; degradation products can be detected only in the presence of reducing agents; the enzyme(s) responsible for degradation is not collagenase itself, but rather a contaminating enzyme(s), presumably a protease(s); and receptor degradation has little effect on the ability of the cells to bind hormone or to respond with increased steroid biosynthesis. Since normal gonadal cells are usually isolated following dispersion of the tissue with collagenase, our results suggest that these cells are likely to bear a degraded (albeit functional) form of the LH/CG receptor, and thus should not be used in studies dealing with the structure of this receptor. |
