Monoclonal antibodies specific for the binding site on the LH receptor alter progesterone production in cultured granulosa cells.

Monoclonal antibodies (mAbs) specific for the LH receptor (LHR) were generated through a modified auto-anti-idiotypic approach in which human chorionic gonadotropin (hCG) was used as the immunogen followed by cyclophosphamide to induce anti-idiotypic antibodies. The purpose of this study was to investigate the effectiveness of these antibodies to alter progesterone production in porcine granulosa cells in vitro. Anti-LHR mAbs were incubated with granulosa cells in the presence or absence of a stimulatory dose of hCG. Progesterone output by treated cells was measured using a RIA procedure. Most of the mAb could inhibit stimulated progesterone production by cultured granulosa cells. It was speculated that two possible mechanisms may cause the inhibition effect observed. Several of the antibodies appeared to block hCG binding thus removing the stimulatory effects of hCG. However, the most potent inhibiting mAbs for progesterone production had little or no effect on hCG binding, suggesting that some other mechanism was responsible for the observed inhibition. In addition, several of the antibodies were found to have a stimulatory effect on progesterone production by granulosa cells even in the absence of a stimulating dose of hCG. It is proposed that these antibodies were able to mimic hCG.

Purines inhibit the development of mouse embryos in vitro.

The first cleavage of embryos derived from random-bred, inbred, and hybrid-inbred female mice was not arrested by purines at concentrations as high as 30 microM. Development after the first or second cleavage was arrested by hypoxanthine, adenosine or inosine, but not guanosine. In agreement with previous results, the purine-induced block was reversed when arrested embryos were transferred to purine-free media after 24 h in culture. The cleavage arrest was not due to elevations of cAMP as a result of inhibition of phosphodiesterase activity since similar concentrations of phosphodiesterase inhibitors or dibutyryl cAMP did not block development. Treatment with inhibitors of enzymes that convert IMP to AMP or to GMP did not reverse the hypoxanthine-induced block, thus demonstrating that mitotic arrest is mediated by a mechanism different from the hypoxanthine arrest of meiosis. Thymidine incorporation studies showed that the block did not prevent the onset of DNA synthesis. The results reveal a profound sensitivity to purine inhibition of a cell process that occurs during the first 30 h of mouse embryo development and is necessary for progession through the G2 or M phases of the second or third cleavage.