Estradiol, Progesterone and Cyclic-Nucleotides in the Fluid of Persistent Follicles and Follicles from the Luteal Phase of Sexual Cycle of Cows

Veterinarni Medicina 36, 1991, 649-655

The objective of the present study was to compare the concentrations of 17 beta-estradiol, progesterone, cyclic adenosine monophosphate and cyclic quinosine monophosphate in the largest follicles of cows that persist for seven days after insemination following the preceding synchronization of oestrus and superovulation and in follicles of the luteal phase of cycle (5th-10th days). Animals included in the experiment were selected on the basis of rectal examination. Synchronization of oestrus was achieved in 24 crossbreds of Slovak Pied X Lowland Black Pied breeds (SS X NC) using two doses of cloprostenol of Czechoslovak provenience Oestrophan Spofa, 500-mu-g in each, within 11 days. Serum gonadotrophin at the amount of 2500 I. U. was administered forty-eight hours before administration of the second dose PGF2 alpha. Experimental animals were inseminated after 72 hours. On the 7th day after mating the cows were killed at a slaughterhouse. Evaluated were only the ovaries of the 14 cows in which the persistant large follicles occurred. Ovaries of the 13 control cows in the luteal phase between the 5th-10th days were obtained at the slaughterhouse by the method after Ireland et al. (1980). Correct determination of the phase of sexual cycle was substantiated by determination of progesterone concentrations in blood serum. Follicular fluid was obtained from the largest follicles by aspiration and centrifuged in a cooled centrifuge at 3000 G. The concentrations of 17 beta-estradiol and progesterone in follicular fluid were determined using kits from URVJT at Kosice, designated RIA-test-ESTRA (SI-125-9) or RIA-test-Prog (SI-125-6). Concentrations of cyclic nucleotides were determined by RIA kits from UVVVR (Prague), designated cAMP125J RIA (RIO12) and cGMP125J RIA (RIO42). The method after Callesen et al. (1986), based on expression of the index of progesterone and 17 beta-estradiol ratio, was used to determine steroidal dominance of follicles. Average concentrations of 17 beta-estradiol in the luteal phase of physiological sexual cycle within days 5-10 were higher in progesterone-dominant follicles (48.3 +/- 22.2 nmol.l-1), compared to persistent follicles (9.15 +/- 5.47 nmol.l-1). Average concentrations of progesterone in follicular fluid were significantly higher in persistent follicles (4751.8 +/- 1134.4 nmol.l-1) than in the population of large, progesterone-dominant follicles from the 5th to the 10th day of physiological sexual cycle (1189.0 +/- 488.2 nmol.l-1) at the level P < 0.05 (Fig. 1). Average concentrations of cAMP in progesterone-dominant follicles in the luteal phase of physiological sexual cycle (35.4 +/- 8.9 nmol.l-1) were significantly higher than in persistent follicles (4.9 +/- 1.2 nmol.l-1) at the level P < 0.05. There were no differences in cGMP concentrations between both groups (Fig. 2). The higher average concentrations of progesterone in follicular fluid and low concentrations of cAMP in animals subjected to treatment with serum gonadotrophin, in comparison with follicles obtained during the physiological sexual cycle, suggest the premature luteinzation of follicles presumably due to the long half-life of serum gonadotrophin (Y a d a v et al., 1986), which has a negative influence on the growth and development of follicles. Our observations indicate that serum gonadotrophin not only stimulates the growth of follicles but also influences markedly the steroidogenic capability of growing follicles. Deviations of physiological changes in functionality of the adenylate-cyclase system and resulting steroidogenesis of preovulation follicles due to the used gonadotrophin can have a negative effect on the full value of produced oocytes and their ability to ovulate

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