Concentration of gonadotrophins in the plasma of sheep given gonadal steroid antisera to raise ovulation rate

Pathiraja, N.; Carr, William; Fordyce, Marjorie; Forster, J. R. M.; Land, R. B.; Morris, Brian

doi:10.1530/jrf.0.0720093

Cited by 23 publications

(14 citation statements)

References 8 publications

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“…Immunization against oestradiol or oestrone, during the luteal or follicular phase, leads to an increase in the frequency of LH pulses and an increase in ovulation rate (Scaramuzzi & Radford, 1983;Pathiraja et al, 1984). Conversely, exogenous oestradiol, in the form of an implant, is known to decrease the ovulation rate of ewes (Webb & Gauld, 1987).…”

Section: Introductionmentioning

confidence: 99%

LH, FSH and ovulation rate in ewes treated with exogenous oestradiol

Atkinson

Adams²,

Martin³

1989

Reproduction

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Summary. In two experiments, mature Merino ewes were fitted with subcutaneous implants containing oestradiol-17\g=b\ or empty implants (control). Peripheral concentrations of LH and FSH were measured during luteal and follicular phases, which were synchronized by means of intravaginal progestagen-impregnated sponges. The ovulation rates of the ewes were determined by laparoscopy, 1 week after luteolysis. In Exp. 1, small implants (3 mm) decreased the LH pulse frequency before luteolysis. In the ewes with oestradiol implants, the amplitude of the preovulatory surge of LH was reduced and the onsets of the LH and FSH surges were delayed. There was no effect of oestradiol on LH baseline, LH pulse amplitude or in the concentration of FSH during the luteal or follicular phases. In Exp. 2, larger implants (10 mm) were inserted for the luteal, follicular, or luteal + follicular phases. The control ewes had empty implants. In the ewes with oestradiol implants, LH pulse frequencies were decreased during the luteal phase. This decrease persisted throughout the follicular phase, even though the oestradiol implants had been removed. There were no differences in the other measures of LH or FSH in the luteal or follicular phases. Ovulation rates were not affected by oestradiol treatment in either experiment, indicating that the regulation of LH pulse frequency is not a critical factor in the determination of ovulation rate in ewes. This was supported by retrospective analysis of the gonadotrophin profiles of single and twin-ovulating ewes, in which all measures of LH were similar between the two groups. However, twin-bearing ewes had slightly higher circulating concentrations of FSH during the luteal phase. As the difference in FSH was not large (13%), and it disappeared after luteolysis, it is difficult to postulate that FSH plays a major role in the final selection of the preovulatory follicle(s) in the ewe.

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Section: Introductionmentioning

confidence: 99%

LH, FSH and ovulation rate in ewes treated with exogenous oestradiol

Atkinson

Adams²,

Martin³

1989

Reproduction

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“…Animals immunized against oestrogens, androgens and progesterone all have increased concentrations of LH associated with increases in LH pulse fre¬ quency and/or amplitude (Martensz et ai, 1979;Pathiraja et ai, 1984;Thomas et ai, 1987;Campbell, 1988). FSH concentrations, however, are elevated in oestrogen-immune animals (Martensz et ai, 1979;Pant, 1978;Pathiraja et al, 1984) but are usually unchanged or depressed in androgen-immune ewes (Martensz et ai, 1979;Pathiraja et ai, 1984;Campbell, 1988 (1980) found that oestradiol concentrations in ovarian venous plasma during the follicular phase were actually higher in androstenedione-immune ewes. This finding led to the postulation that androstenedione may exert its own feedback effects on LH secretion.…”

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confidence: 99%

Steroid secretion rates and plasma binding activity in androstenedione-immune ewes with an autotransplanted ovary

Campbell

Scaramuzzi²,

Downing³

et al. 1990

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Summary. Mature Merino ewes in which the left ovary and its vascular pedicle had been autotransplanted to the neck were divided into control (N = 5) and immunized groups (N = 6). The immunized ewes were treated (2 ml s.c.) with Fecundin\s=r\1 and 4 weeks before the start of blood sampling. Ovarian and jugular venous blood was collected every 10 min at two stages of the follicular phase (21\p=n-\27 h and 38\p=n-\42h after i.m. injection of 125 \g=m\g of a prostaglandin (PG) analogue) and during the mid-luteal phase (8 h at 15-min intervals). The ewes were monitored regularly for luteal function and preovulatory LH surges. Hormone concentrations and anti-androstenedione titres were assayed by RIA and ovarian secretion rates of oestradiol-17\g=b\,progesterone and androstenedione were determined.After the booster immunization, progesterone increased simultaneously with titre in immunized ewes, reaching 30 ng/ml at the time of PG injection when median titre was 1:10 000. All ewes responded to PG with LH surges 42\p=n-\72h later: 2 of the immunized ewes then had a second LH surge within 3\p=n-\4 days at a time when peripheral progesterone values were 2\p=n-\3ng/ml. The frequency of steroid and LH pulses was greater in immunized ewes (P < 0\m=.\05)during the luteal phase but not the follicular phase. The secretion rate of androstenedione was 6\p=n-\10 times greater (19\p=n-\37ng/min; P < 0\m=.\001) in immunized ewes at all sampling stages. Progesterone secretion rates were 3 times greater (16 \g=m\g/min; P < 0\m=.\001)during the luteal phase in immunized ewes. The amplitude of oestradiol pulses was significantly reduced in immunized ewes (4\m=.\8 vs 2\ m=. \ 1ng/min at +24 h and 6\m=.\5 vs 2\ m=. \ 8ng/min at +40 h in control and immunized ewes, respectively: P < 0\m=.\05)during the follicular phase. However, the mean secretion rate of oestradiol at each phase of the cycle was not significantly different between treatment groups. Analysis of bound and free steroid using polyethylene glycol showed that >98% of peripheral and ovarian venous androstenedione and 86% of peripheral progesterone was bound in immunized ewes but there was no appreciable binding (<0\m=.\1%) in control ewes. Similarly, 50% of ovarian venous oestradiol was bound in immunized ewes compared to 15% in control ewes.We conclude that immunization against androstenedione increases the secretion rate of androstenedione and progesterone but not of oestradiol. The enhanced plasma binding of progesterone and oestradiol in androstenedione-immunized ewes may interfere with the biological action of these steroids, thus providing an explanation for the elevated LH pulse frequently observed in immunized ewes.

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“…Concentrations of FSH, in contrast to LH, were mostly unchanged or even decreased in A 4 -immunized ewes [ 1,[3][4][5]. As the ova rian sensitivity to exogenous gonadotropins, in terms of cAMP production, was not affected by A4-immunization [4], Campbell et al [5] concluded that FSH was not responsible for the increased ovulation rate in A 4 -immunized ewes.…”

Section: Discussionmentioning

confidence: 99%

“…Increased P concentration was also a common feature in the A 4 -immunized ewes, however the increase was confined to the luteal phase [5,15]. Plasma concentrations of FSH were generally unchanged or even decreased by A4-immunization [1,[3][4][5] w i t h o n e n o t a b l e e x c e p t i o n [ 1 5 ] , w h e r e immunization against A 4 increased plasma concentrations of FSH during the luteal phase. Do 3α-diol immunization and A4-immunization increase the ovulation rate by a similar mechanism?…”

Section: Discussionmentioning

confidence: 99%