The Gonadotrophic Hormone Response of Anoestrous and Cyclic Ewes to Synthetic Luteinizing Hormone-Releasing Hormone

Symons, A. M.; Cunningham, N. F.; Saba, N.

doi:10.1530/jrf.0.0390011

Cited by 31 publications

(15 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The releases of LH observed in response to Gn-RH are in agreement with other studies (Foster & Crighton, 1973) and are similar to Gn-RH-evoked releases in anoestrous and spayed ewes (Reeves et al, 1972;White, Hedlund, Rippel, Arnold & Flouret, 1973 ;Radford & Wallace, 1974;Symons, Cunningham & Saba, 1974). The pattern of release of LH was similar on Days 12 and 25 after lambing, but significantly more was released at the later time, indicating a change in pituitary sensitivity to Gn-RH, a change in pituitary content of LH, or increased synthesis.…”

Section: Discussionsupporting

confidence: 89%

Studies of pituitary function in lactating ewes

Restall¹,

Kearins²,

Starr³

1977

Reproduction

View full text Add to dashboard Cite

The release of LH from the pituitary of lactating ewes was studied. In Exp. 1, ewes were injected with 50 microng oestradiol benzoate (OB), 2-0 mg testosterone propionate (TP) or oil only (control) on days 5, 10, or 20 after lambing. LH was measured in peripheral plasma samples obtained 20-38 h after treatment, and the ovulations were recorded. The number of ewes in which an LH release was detected, and the amount released, declined between Day 5 and 20 after OB treatment but increased after TP treatment. The releases of LH were not always accompanied by ovulation and the incidence of ovulation was higher in ewes treated with TP. In Exp. 2, lactating ewes were injected with 1 or 5 (at 2-h intervals) doses of 50 microng Gn-RH, on Days 12 or 25 after lambing. LH was measured in peripheral plasma samples collected every 2 h for 10 h and every 3 h for a further 70 h. Release of LH occurred in all ewes, the amount being greater in ewes receiving multiple injections and in ewes treated on Day 25. The incidence of ovulation was higher after treatment on Day 25. Multiple injections of Gn-RH appeared to reduce the incidence of abnormal corpora lutea.

show abstract

Section: Discussionsupporting

confidence: 89%

Studies of pituitary function in lactating ewes

Restall¹,

Kearins²,

Starr³

1977

Reproduction

View full text Add to dashboard Cite

show abstract

“…Similar biphasic responses to infusions of LH-RH have been observed in man (Bremner & Paulsen, 1974) and to a certain extent in the rat , and have been proposed as evidence for the existence of two pools of LH. In the rat, LH levels decline after a few hours of infusion, and a similar termination of responsiveness to infused LH-RH has been observed in the sheep, though a biphasic response was not described (Chakraborty, Adams, Tarnavsky & Reeves, 1974;Symons, Cunningham & Saba, 1974;Shareha, Ward & Birchall, 1976). Such a decrease during the course of the infusions in the present study on the guinea-pig was not observed, possibly because of the relatively short period of infusion.…”

Section: Discussionsupporting

confidence: 75%

Luteinizing Hormone Responsiveness to Luteinizing Hormone Releasing Hormone in the Adult Guinea-Pig: Direct Ovarian Involvement

Haar¹

1978

Journal of Endocrinology

View full text Add to dashboard Cite

The effects of intravenous injection of synthetic luteinizing hormone releasing hormone (LH-RH) on the release of LH and FSH have been studied in the adult guinea-pig. In all the experiments the secretion of FSH was apparently unaffected by administration of LH-RH. The release of LH was log dose-dependent over the range 0\m=.\5\p=n-\50 \ g=m\ g LH-RH.During the female cycle, the maximum increment in the concentration of LH after a single i.v. injection of 0\m=.\5 \g=m\g LH-RH decreased progressively from day 1 to day 13. Double or triple injections of 1 \g=m\g LH-RH at 1 h intervals produced no potentiation on day 3 but progressively greater LH responses occurred on days 7, 10 or 13 of the oestrous cycle. Ovariectomy immediately before the first injection of LH-RH on day 7 blocked the potentiated response to subsequent injections, whereas ovariectomy immediately before the second injection still permitted this potentiation. These results suggest that there is direct ovarian involvement in the potentiated response to LH-RH observed during the later part of the guinea-pig oestrous cycle.Infusion of LH-RH (1 \ g=m\ g over 200 min) produced a potentiated release of LH in female guinea-pigs on day 7 (but not on day 3) of the oestrous cycle after a delay of 1\m=.\5h. It is proposed that there are two 'pools' of LH in the pituitary gland of the female guinea-pig and that the second pool is 'activated' consequent upon previous hypophysial stimulation of secretion from an ovary containing adequately developed follicles.Luteinization or ovulation can be induced in guinea-pigs by two injections of LH-RH administered 1 h apart after day 7 of the cycle ( . T. Donovan, personal communication). Animals were therefore treated on days 7, 10 or 13 with two i.v. injections of 1 µg LH-RH (2 µg/ml) each flushed in with 0-5 ml physiological saline) 65 min apart. Blood samples were collected 10, 20 and 30 min before and 7, 15, 25, 35, 45 and 55 min after the first injection and 7, 15, 25, 35, 45, 55, 70, 85, 100, 115, 130, 145, 160, 175 and 190 min after the second injection of LH-RH.

show abstract

“…The ovary during anoestrus contains follicles which appear macroscopically similar to the follicles present during the breeding season (Cole & Miller, 1935;Kammlade, Welch, Nalbandov & Norton, 1952;Mallampati & Casida, 1970;Roche et al 1970). The concen¬ trations of oestradiol (Reeves, Tarnavsky & Chakraborty, 1974;Yuthasastrakosol et al 1975) and progesterone (Symons, Cunningham & Saba, 1974;Yuthasastrakosol et al 1975) measured in peripheral plasma are low during anoestrus. During the breeding season, oestradiol and androstenedione are secreted almost entirely from the follicular compart¬ ment of the ovary ).…”

Section: Discussionmentioning

confidence: 94%

Androstenedione and the Control of Luteinizing Hormone in the Ewe During Anoestrus

Martensz¹,

Baird²,

Scaramuzzi³

et al. 1976

Journal of Endocrinology

View full text Add to dashboard Cite

Androstenedione and oestradiol were measured by radioimmunoassay in the utero-ovarian venous plasma of two ewes during anoestrus. The concentrations of both steroids were significantly higher than the corresponding concentrations in peripheral plasma, indicating that androstenedione and oestradiol are secreted by the ovary during anoestrus. The concentration of LH during anoestrus was measured by radioimmunoassay in jugular venous plasma of control ewes, ewes immunized against 11alpha-OH-androstenedione-bovine serum albumin and ewes that had been ovariectomized and hystrectomized 9 months previously. During a 12 h sampling period, discharges of LH occurred more frequently in the immunized ewes than in the control group but less frequently than in the ovariectomized group. The frequency of discharge was positively correlated with the titre of androstenedione antibodies in the immunized animals. After injection of 25 mug oestradiol benzoate (OB) all controls, 3 out of 5 immunized and 4 out of 5 ovariectomized-hysterectomized ewes showed positive feedback. No positive feedback occurred in the two ewes with the highest antibody titres to androstenedione, but negative feedback in response of OB apperaed to function normally in all the androstenedione immunized sheep. It is postulated that androstenedione, or one of its metabolites, normally modulates the effects of oestradiol in the control of gonadotrophin secretion in the ewe.

show abstract

The Gonadotrophic Hormone Response of Anoestrous and Cyclic Ewes to Synthetic Luteinizing Hormone-Releasing Hormone

Abstract: Summary. Anoestrous and cyclic ewes were treated with luteinizing hormone-releasing hormone (LH-RH) by intravenous (i.v.)

Cited by 31 publications

References 7 publications

Studies of pituitary function in lactating ewes

Studies of pituitary function in lactating ewes

Luteinizing Hormone Responsiveness to Luteinizing Hormone Releasing Hormone in the Adult Guinea-Pig: Direct Ovarian Involvement

Androstenedione and the Control of Luteinizing Hormone in the Ewe During Anoestrus

Contact Info

Product

Resources

About