Changes in FSH and the pulsatile secretion of LH during treatment of ewes with bovine follicular fluid throughout the luteal phase of the oestrous cycle

Wallace, Jean E.; McNeilly, Alan S.

doi:10.1677/joe.0.1110317

Cited by 51 publications

(25 citation statements)

References 33 publications

(44 reference statements)

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“…This is surprising, as it is widely accepted that FSH plays a major role in the conversion of androgens to oestradiol-17ß (Baird, 1977;Dorrington & Armstrong, 1979), and that oestradiol-17ß is the princi¬ pal ovarian steroid contributing to negative feedback in the sheep (Baird & McNeilly, 1981 (McNeilly, 1984(McNeilly, , 1985. However, after an extended period ( > 3 days) of bFF treatment, there is a significant increase in both the frequency and the amplitude of LH episodes (Wallace & McNeilly, 1986 (Martin, 1984). In the present experiment, the rams had been introduced more than 14 days earlier.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, LH, but not FSH, appears to be responsible for the induction of ovulation in seasonally anoestrous ewes treated with low doses of GnRH (McLeod et al, 1982(McLeod et al, , 1983McLeod & Haresign, 1987). Wallace & McNeilly (1986) In seasonally anoestrous ewes, a prolonged period of treatment with low doses of GnRH will consistently induce development of preovulatory follicles which culminates in ovulation (Hunter et al, 1986). In the current experiments, GnRH-treated seasonally anoestrous ewes were used to monitor the final stages of development of the preovulatory follicle.…”

Section: Introductionmentioning

confidence: 99%

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Suppression of plasma FSH concentrations with bovine follicular fluid blocks ovulation in GnRH-treated seasonally anoestrous ewes

McLeod

McNeilly²

1987

Reproduction

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Summary. The specific requirement for FSH in the final stages of preovulatory follicle development was assessed in seasonally anoestrous ewes given 2-h injections of GnRH (250 ng/injection), with (N = 10) or without (N = 10) concurrent treatment with bovine follicular fluid (bFF: 2 ml given i.v. at 8-h intervals). Treatment with bFF significantly (P < 0\m=.\01)suppressed plasma FSH concentrations, but, at least for the first 30 h of treatment, did not influence the magnitude of GnRH-induced LH episodes (mean max. conc. 3\m=.\00 \ m=+-\ 0\m=.\39and 3\m=.\63 \ m=+-\ 0\m=.\51 ng/ml for bFF-treated and control ewes, respectively). Of 10 animals treated with GnRH for 72 h, 5/5 control ewes showed oestrus and ovulated whereas 0/5 bFF-treated ewes showed oestrus or ovulated in response to GnRH treatment. There was, however, a transient (13\m=.\2\m=+-\ 1\m=.\0h) increase in plasma LH concentrations in the ewes given bFF (mean max. conc. 4\m=.\64\m=+-\1\m=.\57 ng/ml), which was coincident with the preovulatory LH surge recorded in animals given GnRH alone. In 10 GnRH-treated ewes slaughtered after 32 h of treatment, the mean diameter of the largest antral follicle was significantly (P < 0\m=.\001) greater in control ewes (5\m=.\92 \m=+-\0\m=.\17 mm) than in animals that were also given bFF (3\m=.\94\ m=+-\ 0\m=.\14 mm). In addition, the incidence of atresia in the 3 largest antral follicles present at this time was greater in bFF-treated ewes. These results show that, when plasma FSH concentrations are suppressed by administration of bFF, although the magnitude of GnRH-induced LH episodes is unchanged, preovulatory follicular development is impaired and ovulation does not occur. This may be indicative of a specific requirement for FSH in the final stages of preovulatory follicle development, or due to direct inhibitory effects of bovine follicular fluid.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Suppression of plasma FSH concentrations with bovine follicular fluid blocks ovulation in GnRH-treated seasonally anoestrous ewes

McLeod

McNeilly²

1987

Reproduction

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“…It appears that progesterone does not affect LH pulse frequency in this species unless it is present in the plasma at concentrations of > 3 ng/ml (Sutherland, 1987) and so the implants were inadequate to test fully the role of progesterone in negative feedback. Again, it is most likely that the goat and ewe are similar, with LH pulse frequency controlled during the luteal phase by a synergistic interaction between progesterone and oestradiol (Martin et al, 1983;Wallace & McNeilly, 1986). The differences between the species are therefore quantitative rather than qualitative, a supposition which should be tested by studies incorporating dose-responses for the steroids.…”

Section: Methodsmentioning

confidence: 99%

Seasonal and hormonal control of pulsatile LH secretion in the dairy goat (Capra hircus)

Chemineau¹,

Martin²,

Saumande³

et al. 1988

Reproduction

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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 6h) 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\x=req-\ 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.

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“…Group 1 (n=8) were treated with FSH (5 µg/h) for 3 days without LH and Group 2 (n=10) were treated with FSH (5 µg/h) for 3 days with LH (2·5 µg administered as a bolus injection every 4 h). This dose of LH has been shown to induce an LH pulse of similar magnitude to that observed during a normal luteal phase (Baird et al 1976, Wallace & McNeilly 1986, Whisnant et al 1991. Ovarian (5 ml) and jugular (3 ml) venous blood samples were taken every 4 h over the experimental period and there were three periods of intensive blood sampling 24, 48 and 72 h after the start of FSH infusion.…”

Section: Experimental Designmentioning

confidence: 99%

Ovarian function in ewes made hypogonadal with GnRH antagonist and stimulated with FSH in the presence or absence of low amplitude LH pulses

Campbell

Dobson²,

Scaramuzzi³

1998

Journal of Endocrinology

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This study examined the effect of LH pulses, of similar amplitude and frequency to those found in the luteal phase, on the pattern of hormone secretion and follicle development in GnRH antagonist-suppressed ewes stimulated with exogenous FSH. This experiment was conducted on ewes with ovarian autotransplants in a continuous study. Follicle development was suppressed in 18 ewes by 3 weeks of GnRH antagonist treatment (50 µg/kg per 4 days s.c.), and was then stimulated by infusion of ovine (o)FSH (5 µg NIADDK-oFSH-16/h i.v.) for 3 days. In addition to FSH, 10 animals received pulses of LH (2·5 µg NIADDKoLH-26 i.v.) every 4 h for the entire period of the FSH infusion. The follicle population was determined by daily ultrasound. Samples of ovarian and jugular venous blood were collected at 4-h intervals over the period of the FSH infusion and there were three periods of intensive blood sampling (15-min intervals for 2·5 h at 24, 48 and 72 h after the start of the FSH infusion) when the steroidogenic capacity of the follicles in all 18 ewes was tested around an LH challenge (2·5 µg i.v.).GnRH antagonist treatment resulted in a 57% decrease in FSH concentrations and prevented ovarian follicle development beyond 3 mm in diameter. Infusion of FSH resulted in a 60% increase in FSH concentrations and stimulated the development of large antral follicles and a coincident increase in ovarian androstenedione, inhibin and oestradiol secretion in both experimental groups. In the absence of 4-hourly LH pulses basal steroid secretion was negligible (<1 ng/min; P<0·001). Daily LH challenges, however, revealed no difference in the steroidogenic capacity of the follicle population in either experimental group. Similarly, LH pulses had no effect on the growth rate and number of antral follicles stimulated by FSH infusion, or the pattern of ovarian inhibin secretion.In conclusion, these results show that while FSH alone can stimulate the development of ovulatory sized follicles in ewes made hypogonadal with GnRH antagonist, physiological patterns of LH stimulation have no deleterious effects on FSH-stimulated follicle development and are essential for normal steroidogenesis.

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Changes in FSH and the pulsatile secretion of LH during treatment of ewes with bovine follicular fluid throughout the luteal phase of the oestrous cycle

Cited by 51 publications

References 33 publications

Suppression of plasma FSH concentrations with bovine follicular fluid blocks ovulation in GnRH-treated seasonally anoestrous ewes

Suppression of plasma FSH concentrations with bovine follicular fluid blocks ovulation in GnRH-treated seasonally anoestrous ewes

Seasonal and hormonal control of pulsatile LH secretion in the dairy goat (Capra hircus)

Ovarian function in ewes made hypogonadal with GnRH antagonist and stimulated with FSH in the presence or absence of low amplitude LH pulses

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