Steroidogenesis by Bovine Theca Interna in an In Vitro Perifusion System

Abstract

The steroidogenic responses of perifused bovine theca interna to varying flow rates of media and varying amounts of luteinizing hormone (LH) were examined and the steroidogenic outputs of theca interna from follicles of differing size and health were compared with those of other ovarian tissues. The outputs of androstenedione by thecae interna from healthy but not atretic follicles, with or without stimulation by LH, were amplified by the flow rate of media. Steroidogenesis by perifused theca interna was also influenced by the mass and concentration of LH as well as by the duration of exposure to LH. When expressed on a per unit mass basis, the outputs of androstenedione from LH-primed thecae interna from small (2-5.5 mm diameter), medium (6-9.5 mm diameter) and large (.gtoreq. 10 mm diameter) healthy follicles were comparable. But when the above data were expressed per total mass of theca interna, the androstenedione output increased significantly with increasing follicular diameter (P < 0.01). Under the experimental conditions employed, the fraction of androstenedione produced by thecal tissue as a percentage of the total output of progesterone, androstenedione, testosterone and estradiol was 82%, whereas the progesterone, testosterone and estradiol fractions were 1, 15 and 2%, respectively. By contrast, the granulosa cell output of progesterone, androstenedione, testosterone and estradiol was 79, 0, 0 and 21%, respectively. When this cell type was supplied with saturating amounts of androstenedione, it contributed .gtoreq. 90% of the total quantity of estradiol by the 2 cell types in isolation.