Regulation of Cholesterol Acquisition and Utilization in the Corpus Luteum

Abstract

The enzymatic reactions involved in the formation of progesterone in the corpus luteum have been known for some time, but the factors which control the synthesis and secretion of this hormone are not fully understood (Strauss et al., 1981). Two aspects of the steroidogenic process deserve attention as loci for regulation by gonadotropins or other substances; the acquisition of the substrate, cholesterol, and cholesterol side chain cleavage, which is generally accepted as a rate-determining step. Because functional luteal cells produce relatively large quantities of steroid, they must have an efficient means of obtaining cholesterol. Recent studies we have carried out demonstrate that lipoprotein-carried cholesterol is the primary substrate for rat luteal tissue and that specific, saturable binding sites mediate the uptake of high density lipoprotein sterol (Christie et al., 1979; Schuler et al., 1979; Schuler, Toaff and Strauss, 1981; Rosenblum et al., 1981; Schuler et al., 1981a; Christie et al., 1981). Just how the number of lipoprotein receptors on luteal cells is regulated has not yet been defined.