Steroidogenesis in Theca Cells of Chicken Follicles

The aim of this study was to assess and compare the steroidogenic response to luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in cells of the theca interna and theca externa isolated from follicles at different stages of maturation. Cells of the theca interna and theca externa isolated from the largest, second largest and third-fifth largest preovulatory follicles of the chicken (Gallus domesticus) were incubated at the concentration of 2 x 10 5 cells/ml/tube in Medium 199 containing 10mM Hepes and 0.2% bovine serum albumin with increasing doses (0, 0.1, 1.0, 10 and 100 ng/ml/tube) of ovine LH (oLH) or ovine FSH (oFSH). After the 4 hr-incubation, progesterone (P4), testosterone (T), and estradiol-17 (E2) in the medium were measured by RIA. P4 and T were detected in cultured medium of theca interna cells but were undetectable  25pg/tube) in that of theca externa cells, while E2 was detected in cultured medium of theca externa cells but not (< 25 pg/tube) in that of theca interna cells. The productions of P4 and T were stimulated in a dose dependent manner by oLH and oFSH. The responses to oLH and oFSH were greater in smaller follicles, although the response to oFSH was less than that to oLH. E2 production was stimulated in a dose-dependent manner by oFSH with greater response in smaller follicles but not by oLH. The present results support a three-cell theory for estrogen production in avian follicles and indicate that, in the chicken, the smaller follicles may play a conspicuous role in gonadotropin-induced steroidogenesis.