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Estradiol-17β Biosynthesis by the Early Bovine Fetal Ovary During the Active and Refractory Phases

1980; Oxford University Press; Volume: 23; Issue: 3 Linguagem: Inglês

10.1095/biolreprod23.3.577

1529-7268

Mordechai Shemesh,

Estrogen and related hormone effects

Estradiol-17i3 biosynthesis was studied by radioimmunoasssy during the “active” phase of ovaries of early bovine fetuses of 5-8 cm crown-rump length (CRL) (n = 40) and during the “refractory” phase of ovaries of fetuses of 10-20 cm CRL (n = 85). The mean value of estradiol17f3 secreted by the incubated ovaries of the early active phase was 1.5 ± 0.4 ng/ovary/24 h (mean ± SEM), and in the presence of bovine LH estradiol-1713 secretion was significantly enhanced (4.2 ± 0.6, P<0.OO1). In the presence or absence of LH, estradiol-17�3 was undetectable in the incubated ovaries of the refractory phase. Addition of testosterone to the incubation medium significantly enhanced estradiol-17(3 production (P<0.001) by ovaries of both the active and refractory phase. In contrast, neither progesterone, DHT, nor 17n-hydroxyprogesterone affected estradiol secretion. In the time-course studies of estradiol-17j3 production in response to testosterone, the incubated active phase ovaries from fetuses of 5-8 cm CRL responded to testosterone within 30 mm, whereas for the refractory phase ovaries a lag period of 10 h was needed. Addition of 8-Br-cAMP caused a significant stimulation after 5 h of both testosterone (P<O.O01) and estradiol (P<0.02) production by the incubated active ovaries, whereas when the inactive ovaries were used only progesterone secretion was significantly enhanced (P<0.0O1). The data suggest that the lack of ovarian aromatizable androgens may play a role in the change from the active to the refractory phase. That ovariesfrom bovine fetuses of 10-20 cm CRL become refractory suggests that the high estrogen level found at the time of the differentiation of the primordial gonad to ovary isof functional significance.