Steroidogenesis despite a variant metabolism in primary cultures of pig granulosa cells.

Enzymic changes in primary cultures of granulosa cells over 9 days were measured and compared with changes occurring during follicular development in vivo. Characteristic of in vivo development of granulosa cells was a large increase in activities of the NADP+-dependent isocitrate, glucose-6-phosphate dehydrogenases and malic enzyme, and smaller increases in the activities of the NAD+-dependent lactate and malate dehydrogenases. In vitro, the NAD+-dependent dehydrogenases increased in activity, while the NADP+-dependent enzymes showed transient or no changes. Despite the uncharacteristic metabolism, granulosa cells in culture could synthesize steroids. Our results suggest that the cells in vitro and in vivo use different metabolic pathways to support syntheses dependent on reducing equivalents.