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 105
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
