STEROID-METABOLISM IN GRANULOSA AND THECA INTERNA CELLS FROM PREOVULATORY FOLLICLES OF DOMESTIC HEN (GALLUS-DOMESTICUS)

The capability of granulosa and theca interna cells, from preovulatory follicles of the domestic hen, to metabolize steroid precursors was e valuated. Granulosa and theca interna cells were isolated from ovarian preovulatory follicles at three different developmental stages: F1, F 3 and F5. Tritiated pregnenolone (P5), progesterone (P4), dehydroepian drosterone (DHEA), androstenedione (A4) and testosterone (T) were empl oyed as precursors and their metabolic products were evaluated. The ma jor metabolite of P5 by granulosa cells was P4, but we also observed l ow amounts of 5 beta-pregnandione. DHEA metabolism by granulosa cells yielded mainly A4, and minute quantities of 5 beta-androstan-3,17-dion e (5 beta-dione) were detected. The only significant metabolite obtain ed in granulosa cells from A4 was 5 beta-dione, whereas T was only tra nsformed into A4. On the other hand, P5 metabolism by theca interna ce lls yielded A4 as the main product, also P4, 17 alpha-OHP4, 17 alpha-O HP5, 5 beta-pregnandione, and DHEA, were found. When DHEA was the prec ursor A4 was produced in higher amounts than 5 beta-dione. A4 was main ly transformed into 5 beta-dione. In similar conditions, T was transfo rmed into A4. These results show that granulosa cells have enzymatic a ctivities of 3 beta-hydroxysteroid dehydrogenase/5-4 isomerase (3 beta -HSD from P5 and DHEA), 17 beta-hydroxysteroid dehydrogenase (17 beta- HSD from T) and 5 beta-reductase (from P5, DHEA and A4). Whereas theca interna cells have enzymatic activities of cytochrome P450c17 (from P 5 and P4), 3 beta-HSD (from P5 and DHEA), 17 beta-HSD (from T) and 5 b eta-reductase (from P4, DHEA and A4). These data support the concept t hat theca interna cells have the ability to synthesize androgens from progestins produced in granulosa cells. In addition, since theca inter na cells did not show the capacity to aromatize androgens suggests tha t interaction between theca interna and theca externa cells occurs in vivo, thus confirming the three cell model for estrogen production. Fu rthermore, the fact that other metabolites were produced both in granu losa and theca interna cells. but in a different extent, suggests that complex mechanisms are participating in the regulation of steroid syn thesis in avian ovary follicles. (C) 1998 Elsevier Science B.V. All ri ghts reserved.