The Steroidogenic Response of Large and Small Luteal Cells to Dibutyryl cAMP and 25-OH-Cholesterol

Abstract

The mammalian corpus luteum consists of two major types of steroidogenic cells based upon size and histological characteristics. In this study, large (>22µ) and small (12–21 |i) luteal cells from day 8 pregnant rats were separated by elutriation after enzyme dissociation. Aliquots of cells were incubated for 4 h at 37°C in Medium 199 (control), medium plus dibutyryl cAMP (cAMP) at 0.5 mM or 5 mM, or medium plus 10 (µg/ml 25-OH-cholesterol. Production of progesterone, testosterone, and estradiol was measured by radioimmunoassay (RIA). Both cell types showed an increase in progesterone and estradiol synthesis when incubated with cAMP; however, the large luteal cells responded to a tenfold lower dose (0.5 mM) of cAMP than did the small cells which required 5 mM for stimulation. CAMP (5 mM) also resulted in an increase of testosterone release from small luteal cells. Progesterone synthesis was enhanced by 25-OH-cholesterol in the large luteal cells. These results suggest that the two cell types differ functionally with respect to steroidogenesis during pregnancy, and that the large luteal cells may be a major source of progesterone production.