RESUMO
The purpose of this study was to evaluate the effect of varying doses of gossypol acetic acid on early bovine embryo development in vitro. One hundred and forty-eight excellent and good quality bovine morulae were randomly cultured in 0, 1.0, 5.0, 10.0, 30.0 mug gossypol acetic acid (GAA) in normal steer serum and Ham's F-10 media. Bovine embryo development was assessed at 12-h intervals for 96 h. Sixty-seven percent of embryos developed in 0 mug GAA to the hatched blastocyst stage, while 43, 19, 4 and 0% had comparable development in 1.0, 5.0, 10.0 and 30.0 mug GAA, respectively. Embryos in 5.0 mug GAA had a delayed development to the blastocyst stage compared to embryos in 1.0 mug GAA. Development time to expanded blastocyst stage was longer for 10.0 mug GAA embryos than 0, and 1.0 GAA-treated embryos. No embryo cultured in 30.0 mug GAA advanced past the morula stage. Final developmental scores were highest for embryos in 0 mug GAA (4.06) and lowest for embryos cultured in 10.0 and 30.0 mug GAA (0.44 and -0.02, respectively). Embryos cultured in higher doses of GAA degenerated sooner than embryos cultured in 0 mug GAA. These data show a dose-dependent detrimental action of GAA on early bovine embryo development and suggest a direct action on the embryo itself.
RESUMO
Progesterone production by the ovine placenta was investigated between d 80 and 115 of gestation. Serum progesterone concentrations in ewes ovariectomized (ovx) on d 75 of gestation were measured throughout the remainder of gestation, and after the ewes were injected with human chorionic gonadotropin (hCG) or saline on d 80 or 115. In addition, cotyledonary tissue was collected from intact ewes sacrificed on d 80 or 115 and progesterone accumulation was determined during 2 h incubation with or without pregnenolone supplementation and in the presence or absence of hCG or dibutyryl cyclic adenosine monophosphate (dbcAMP). Serum concentrations of progesterone in ovx ewes increased from 3.5 +/- .4 ng/ml on d 80 to 16.4 +/- 2.1 ng/ml on d 115 (P less than .05). That increase was coincident with a 1.5-to 4.5-fold increase in progesterone output by placental tissue in vitro. Addition of pregnenolone enhanced progesterone accumulation in all tissue incubations. Addition of dbcAMP increased progesterone accumulation in the incubation medium only when supplemented with pregnenolone. Human chorionic gonadotropin did not increase placental progesterone secretion in vivo or in vitro. The results confirm the enhanced secretion of progesterone by the ovine placenta between d 80 and 115 of gestation and indicate that the increase results primarily from increased secretory capability per unit of placenta. The tropic mechanism controlling the placental secretion of progesterone remains unclear, but the mechanism may involve elevation of intracellular cAMP.