An explanation for the absence of post-parturient ovulation in the ewe

Wa, Chamley; Jm, Brown; Me, Cerini; Cumming, I. A.; Goding,; Jm, Obst; Williams, Adrienne J.; Winfield, C.G.

doi:10.1530/jrf.0.0320334

Cited by 4 publications

(2 citation statements)

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“…The pituitary content of LH is low at parturition but does increase in the following 3 weeks (O'Reilly & Dziuk, 1973 ; Jaume cited by Chamley et al, 1973), and these stores of LH are apparently sufficient for the significant releases reported here. This dis¬ parity may be due to either the low dose of Gn-RH infused (1-5 pg/h) orthe mode of administration used by Chamley et at.…”

Section: Discussionsupporting

confidence: 53%

Studies of pituitary function in lactating ewes

Restall¹,

Kearins²,

Starr³

1977

Reproduction

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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.

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Section: Discussionsupporting

confidence: 53%

Studies of pituitary function in lactating ewes

Restall¹,

Kearins²,

Starr³

1977

Reproduction

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“…While not immediately pertinent to the question of luteolysis, the possible action of PG's on the secretion of progesterone by the placenta is one of obvious importance, especially in relation to the cause of the fall in pro gesterone secretion immediately prior to parturition [19,111].…”

Section: Pregnancymentioning

confidence: 99%

Prostaglandin F<sub>2α</sub>, ‘the' Luteolysin in the Mammal?

Goding¹,

Cumming²,

Chamley³

et al. 1971

Gynecol Obstet Invest

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Part. I: Prostaglandin F₂_Α (PGF_2Α) was shown to be ‘the’ luteolysin in the ewe on the following criteria: (1) Hysterectomy and/or separation of the uterine horn from the ovary bearing a corpus luteum led to prolongation of the oestrous cycle, (2) PGF_2Αshortened the cycle when administered in the midluteal phase, (3) PGF_2Α was identified in uterine venous blood, (4) a mechanism for the transfer of PGF_2Α from the uterine vein to the ovarian artery was shown to exist, (5) the quantitative aspects of the secretion transfer mechanism and luteolytic potency of PGF_2Α were adequate to account for the observed phenomena. Part II: These criteria were applied for evaluation of PGF_2Α as ‘the’ luteolysin in the following species: cattle, goat, horse, pig, guinea pig, rat, hamster, rabbit, monkey, human. On present knowledge, there appeared to be a variation between species from those in which PGF_2Α was probably concerned in luteolysis and those in which the evidence was against such a role. Part III: PGF_2Α was shown to be luteolytic when given by continuous infusion for 3–6 h into the lumen of the uterus in cattle as well as sheep. The minimum effective dose was of the order of 7 g/kg. The application of this finding to artificial insemination programmes was discussed.