Studies on the source of cholesterol used for steroid biosynthesis in cultured Leydig tumor cells

The studies presented herein were designed to determine the source(s) of cholesterol used for steroid biosynthesis in a clonal strain of cultured Leydig tumor cells (designated MA-10). Our results show that, when the cells are placed in medium devoid of extracellular cholesterol and acutely stimulated with human choriogonadotropin, most of the cholesterol used for steroid biosynthesis is derived from intracellular stores. Upon prolonged stimulation, when the intracellular stores are depleted, the cells meet the enhanced demand for cholesterol by increasing de novo synthesis. The presence of low density lipoprotein has little or no effect on the amount of steroid synthesized during acute stimulation, but it enhances the amount of steroid produced during prolonged stimulation by directly providing cholesterol substrate to the cells.