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Twenty five Holstein-Friesian heifers, clinically normal and with regular oestrous cycles, were used for induction of superovulation (PMSG-PGF2alphalpha-Neutralpha-PMSG). Animals were divided into 5 groups receiving: I - detomidine (40 µg/kg b.w.), II - doxazosin (0.2 mg/kg b.w.), III - yohimbine HCL 1% (1 ml/50 kg b.w.), IV - carazolol (0.01 mg/ kg b.w., i.v.), and V – physiological saline (1 ml/50 kg b.w.). The heifers with PGF2alphalpha-induced cycles were treated with the substances 88 hrs after being given a single i.m. injection of 2500 IU PMSG. All animals were examined by ultrasonography, and by the number and size of ovarian follicles > 3 mm in diameter. The follicles were divided into 3 groups according to the diameter. Blood plasma was stored at -20°C until LH, P4, E2 and PGFM analyses. In the control (V) group, two waves of follicle growth were observed. Yohimbine produced a significant blockage of ovulation. The mean number of corpora lutea in the group III was significantly lower than that in the control group (p< 0.02). No significant differences in the number of corpora lutea were observed between the groups I, II and III. The increase in E2 concentrations could be the response to the PMSG treatment with two waves of growth of large follicles before and after ovulation. Pulsatile LH release was altered by yohimbinum injection, however, the greater amplitude of pulses immediately following yohimbinum administration are suggestive of a positive influence of the alpha-2 adrenergic receptors antagonist. Yohimbinum administration did not affect plasma concentration of examined hormones. There was a difference between the plasma levels of LH after the doxazosin injection. Single injection of the stimulators and blockers of adrenergic receptors did not affect superovulatory response in terms of the numbers of CL, unruptured follicles and embryos recovered. The affectivity of artificial insemination was not significantly different between the control group and the detomidinum groups, while in the yohimbinum group it was significantly lower.
The aim of this study was to determine the influence of alpha- and ß-stimulators (alpha-stimulator: detomidinum HCl) as well as blockers (alpha1-blocker: doxazosin, alpha2- blocker: yohimbinum HCL, ß-blocker: carazolol) on bovine granulosa cells culture from preovulatory follicles. The cell culture was passed in TCM 199 medium with 10% FCS and antibiotics. Tested substances were added to the culture medium in different concentrations. The experiment began when at least 80% of the wells were covered (in four well culture dish of NUNCK-DK). The culture medium was collected every 24 h for hormone analysis. Hormone levels of T, E2, and P4 were determined. The culture was used up to 120 hours. Our results showed a decrease in P-4 secretion after detomidinum addition for all tested concentrations. A slight testosterone level increase was seen in the first 24 hours and then its concentration remained at a constant low level. A slight increase in 17-ß estradiol secretion was also observed. After yohimbinum addition, a statistically significant decrease of progesterone was observed for all concentrations tested. No significant changes were observed at other hormones levels when compared with the control. Doxazosin, when added into the culture medium, did not cause any statistically significant changes in hormone secretions. The addition of carazolol caused a significant decrease in progesterone secretion after culturing for 48 hours. Changes observed in other hormones levels did not differ statistically from the control. These results seem to support the hypothesis that drugs stimulating and blocking adrenergic receptors may play some role in ovarian steroidogenesis in cows.
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