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J. Saumande and A. Lopez-Sebastian

Summary. Oestradiol-17β and conjugated oestrone, oestradiol-17β and oestradiol-17α were measured in peripheral plasma of heifers treated with PMSG/PGF-2α to induce superovulation.

Changes in the concentration of each hormone were synchronous, the highest level being near oestrus. For a given number of ovulations the hormone with the highest concentration was total oestradiol-17α, then came total oestrone, total oestradiol-17β and oestradiol-17β. For each oestrogen, the maximum preovulatory concentration measured was significantly correlated with the number of ovulations; the regression line for total oestradiol-17α was twice as steep as that for oestradiol-17β.

It is concluded that in animals treated to induce superovulation assay of total oestradiol-17α gives a better indication of the number of follicles induced to ovulate than does the more conventional assay of oestradiol-17β.

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M. LEMON, J. PELLETIER, J. SAUMANDE and J. P. SIGNORET

I.N.R.A.-Laboratoire de Physiologie de la Reproduction, Nouzilly, 37380 Monnaie, France

(Received 29th May 1974)

The concentrations of a number of reproductive hormones found in the peripheral plasma of the cow around the time of oestrus have been measured by numerous authors: plasma concentrations of progesterone throughout the oestrous cycle (Stabenfeldt, Ewing & McDonald, 1969), LH (Schams & Karg, 1969), oestrogen and progesterone (Henricks, Dickey & Hill, 1971) and LH and progesterone (Henricks, Dickey & Niswender, 1970). These and other reports have paid little attention to the precise onset and duration of oestrus, behaviour being checked at various intervals (usually two or three times a day) before the expected onset.

To obtain a more precise pattern of hormone concentrations around oestrus, we have measured simultaneously LH, oestradiol-17β and progesterone in samples of plasma taken at 2-hr intervals from cows over a period of 5 days. The cows were maintained with a

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J. Testart, G. Kann, J. Saumande and M. Thibier

Summary. Fluorogestone acetate (vaginal sponge for 4 days) and PMSG (i.m. injection at the time of sponge insertion) treatment was administered to seven 3-month-old calves to induce superovulation. Samples of peripheral plasma were taken every 4 h during treatment (4 days) and then every 2 h for 7 days. FSH, LH, oestradiol and progesterone were measured by radioimmunoassays. In all calves oestradiol concentrations increased 24 h after PMSG injection and reached the highest levels (41–502 pg/ml) during the preovulatory surge of both gonadotrophins. The surge of LH and FSH occurred from 12 to 22 h after cessation of treatment. The maximum levels of LH and FSH were 11–72 ng/ml and 23–40 ng/ml respectively and occurred within 4 h of each other. Between 40 and 68 h after the LH peak the concentrations of progesterone began to increase from basal values, reaching 24·0–101·7 ng/ml when the animals were killed. A quantitative relationship was found between plasma oestradiol concentration and the numbers of ovulating follicles. Progesterone levels seemed to be related to the numbers of corpora lutea and also to the numbers of unovulated follicles. Gonadotrophin output was not quantitatively related to ovarian activity or to steroid secretion.

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P. Chemineau, G. B. Martin, J. Saumande and Elisabeth Normant

Summary. In Exp. 1, the changes in pulsatile LH secretion at the onset of the breeding season were observed in 20 intact, mature Saanen does. Blood was sampled every 20 min for 6 h each week from the beginning of August until the onset of ovulatory activity, as evidenced by cycles in plasma progesterone. The first doe ovulated at the end of August and all were cycling by the end of September. As the first ovulation approached, LH pulse frequency increased by 67% and mean levels of LH increased by 47%. These changes were progressive rather than abrupt. In Exp. 2, seasonal changes in the inhibition of pulsatile LH secretion by ovarian steroids were studied in ovariectomized Saanen does. The animals were untreated (N = 4) or given subcutaneous oestradiol implants (N = 4) and blood was sampled every 10 min for 6 h, twice during the breeding season and twice during the anoestrous season. In each season, the second series of samples was taken after the animals had been treated with progesterone, administered by intravaginal implants. Season did not significantly affect LH secretion in goats not treated with oestradiol, but LH pulse frequency was 54% lower during the anoestrous season than during the breeding season in oestradiol-treated goats. Mean LH concentrations were affected in the same manner as pulse frequency, but pulse amplitude was increased by oestradiol treatment in both seasons. Progesterone had no detectable effect on LH secretion in either season. In Exp. 3, the response to repeated melatonin injections at a set time after dawn was investigated in 11 oestradiol-treated, ovariectomized goats. They were placed under a regimen of long days (16 h light:8 h dark) and 1 month later 6 of them were injected daily (10 h after 'dawn') with 2 mg melatonin. The other 5 animals served as controls. Blood samples (every 10 min for 6 h) were taken just before and 38 and 72 days after the start of melatonin treatment. As the experiment progressed, LH pulse frequency increased by 20% in melatonin-treated goats but decreased by 43% in controls. Mean LH values were maintained in melatonin-treated females but decreased in the control group. Melatonin did not affect pulse amplitude.

The results of the experiments with ovariectomized does suggest that seasonal reproductive cycles in the goat are caused by changes in the duration of melatonin secretion at night, which induce alterations in the intensity with which oestradiol inhibits LH secretion. In turn, this may be responsibile for the gradual changes in the frequency of LH pulses observed in entire does. The frequency of LH pulses is one of the most important endocrine signals controlling ovarian activity so would form the final link in the chain connecting environmental and reproductive cycles.

Keywords: LH; goat; melatonin; steroids; season

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L. P. Cahill, J. Saumande, J. P. Ravault, M. Blanc, J. Thimonier, J. C. Mariana and P. Mauléon

Summary. Total follicular populations and peripheral plasma concentrations of LH, FSH, prolactin, oestradiol-17β and progesterone during the preceding cycle were studied in two breeds of sheep (Romanov and Ile-de-France) which differed widely in their ovulation rates (3·2 and 1·5 respectively).

No LH parameters could be correlated with the follicular details measured. The second peak of FSH occurring 20–30 h after the preovulatory surge of LH was significantly larger in the Romanov ewes and the area under this peak was correlated (P < 0·01) with the number of antral follicles present in the ovary 17 days later. This suggests that formation of the antrum during the follicular growth phase is under the control of FSH. The discharge of prolactin preceding the LH peak, although not significantly different between breeds, was correlated with several of the follicular classes measured, including the number of preantral follicles. The peak value of oestradiol-17β measured before the LH peak was significantly higher (P < 0·05) in the Romanov ewes and was correlated with the number of the largest follicles present. There was no significant difference between breeds in the concentration of oestradiol at the onset of oestrus. The progesterone concentration during the luteal phase was highly correlated with the number of preovulatory follicles.

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O. Cazorla, M. Seck, C. Pisselet, C. Perreau, J. Saumande, J. Fontaine, M. de Reviers and M. T. Hochereau-de Reviers

The aim of the present analysis was to determine whether anti-Müllerian hormone concentrations in prepubertal plasma or adult rete testis fluid are related to the number or function of Sertoli cells in rams or to the presence of the Fec B Booroola gene. Twenty rams from two Booroola crosses, differing in their testicular masses were analysed; in each cross, half of the animals were heterozygous carriers of the Fec B gene. The data from rams, during prepuberty and at adulthood during the non-sexual season, were analysed by two-way ANOVA and residual correlations. In 4-week-old intact male lambs, the mean anti-Müllerian hormone plasma concentration was 15 ng ml−1, irrespective of cross, genotype or eCG stimulation; it was significantly negatively correlated with FSH (r = −0.51; P = 0.02; n = 19). In adults, anti-Müllerian hormone was not detectable in plasma and was 0.5 ng ml−1 in rete testis fluid, irrespective of cross or genotype. The total number of Sertoli cells per testis was not related to anti-Müllerian hormone concentration in lamb prepubertal plasma or in adult rete testis fluid. The concentration of anti-Müllerian hormone in adult rete testis fluid was significantly and negatively correlated with the daily production of leptotene primary spermatocytes per testis (r = −0.56; P = 0.02; n = 16). The mean oestrogen concentration in the adult testicular vein was 2 pg ml−1 and was correlated negatively with the rete testis fluid concentration of anti-Müllerian hormone (r = −0.60; P = 0.02; n = 15) and correlated positively with the daily production of leptotene primary spermatocytes per testis (r = 0.53; P < 0.05; n = 19). In conclusion, anti-Müllerian hormone secretion was not correlated with the total numbers of Sertoli cells per testis and cannot be used as a predictor of the number of Sertoli cells. Anti-Müllerian hormone secretions were not affected by the presence of Fec B gene. However, anti-Müllerian hormone secretion could be considered to be inversely related to the daily production of primary spermatocytes by the testis.