Regulation of cholesterol acquisition and utilization in the corpus luteum

In this report we have focused on two aspects of control of corpus luteum function; the regulation of lipoprotein uptake and the modulation of cholesterol side chain cleavage through alterations in the phospholipid milieu. Until recently, a role of gonadotropins in the acquisition of lipoprotein-carried cholesterol had not been generally appreciated. However, it is likely that the regulation expression of cell surface lipoprotein receptors will prove to be an important function of tropic hormones, particularly LH, since luteal cells generate progestins at a substantial rate and must, therefore, have an equally substantial supply of cholesterol. Factors other than gonadotropins may have a function in control of lipoprotein receptors and it would not be surprising if luteolytic factors, such as prostaglandin F2 alpha, are found to diminish lipoprotein-uptake as part of their action in reducing steroidogenesis. The control of mitochondrial pregnenolone synthesis by gonadotropin-induced alterations in phospholipid composition of mitochondrial membranes represents a novel concept. Whether certain polar lipids will emerge with the status of intracellular messengers remains to be seen. In any event, our observations clearly demonstrate the possibility for such a mechanism of control.