Localization and hormonal regulation of the non-specific lipid transfer protein (sterol carrier protein2) in the rat testis

In testis tissue from mature rats the non-specific lipid transfer protein (nsLTP), also called sterol carrier protein2 (SCP2), is concentrated in the Leydig cells and cannot be detected in Sertoli cells or germinal cells. Conclusions were reached after cell fractionation studies with normal testis tissue and after selective destruction of Leydig cells or germinal cells in vivo. The amount of nsLTP (SCP2) in testis tissue increased twofold 48 h after two daily injections of human chorionic gonadotrophin (100 i.u., s.c.) and decreased twofold after plasma luteinizing hormone levels were suppressed to almost undetectable levels with silicone elastomer implants containing testosterone. The specific localization in the Leydig cells and the luteinizing hormone-dependent cellular concentration of nsLTP/SCP2 support the possibility that this protein could play a role in the regulation of steroidogenesis by regulating the availability of cholesterol for the P450 side-chain cleavage enzyme in the mitochondria of Leydig cells.