Bovine cumulus/oocyte complex: quantification of LH/hCG receptors

LH/hCG receptors of the bovine cumulus/oocyte complex were quantified, and their maximum binding capacities and affinity constants were determined by Scatchard analysis. Specific binding of these gonadotropins to receptors in follicles of different sizes was also determined by radiolabeling techniques. A greater number of receptors was observed to be bound to LH than to hCG (P < 0.05); however, affinity constants did not significantly differ (P > 0.05). The results of specific binding of the gonadotropins presented differences in relation to follicle size. Differences in the specific binding values of LH and hCG were verified (P < 0.05), but when submitted to linear regression analysis, presented similar behaviors in relation to follicle size. It is concluded that receptors of bovine cumulus/oocyte complex cells bind specifically to LH/hCG, that binding capacity is inversely proportional to follicle size, and that the behavior of hCG is similar to that of LH, suggesting that hCG can also promote the maturation of bovine oocytes when used in concentrations greater than LH.