PROGESTERONE REGULATION OF LUTEINIZING-HORMONE RECEPTORS ON CULTURED BOVINE LUTEAL CELLS

During development of the corpus luteum (CL), the numbers of luteinizing hormone (LH) receptors increase. Cultured bovine luteal cells from developing and mature CL were used to examine the influence of progesterone (P(4)) on this receptor. CL were obtained from dairy cows during the early or middle phase of the estrous cycle. In early CL, the number of receptors per cell was increased by exogenous progesterone treatment but there was no effect on receptor numbers in cells from midcycle CL. Binding affinities did not change with respect to age or treatment. Forskolin elevated endogenous progesterone and also enlarged the receptor population. The action did not appear to be an unmasking of cryptic receptors since the effect was not seen in luteal particulates. Elevation of LH receptor numbers by progesterone in immature CL may be a form of intraluteal regulation contributing to the functional maturation of these steroidogenic cells.