Ovarian function in pigs following hypophysial stalk transection or hypophysectomy

Endocrinology of parturition in the pig

“…Since pregnancy was continued when progesterone was given after hypophysectomy (du Mesnil du Buisson and de Namurs, 1969) and since pycnotic corpora lutea were present in hypophysectomized sows (Kraeling and Davis, 1974), it was natural to conclude that a pituitary luteotrophic factor is necessary to maintain normal corpus luteum function in pregnancy. The hypophyseal luteotrophic factor had been suggested long ago to be LH (Brinkley et al, 1964;Anderson et al, 1967;Cook et al, 1967). It was not until recently that our group (Parvizi et al, 1976) found a very peculiar relationship between prepartal circulating LH and progesterone levels (Fig.…”

Oestradiol administration raises luteal LH receptor levels in intact and hysterectomized pigs

“…Increased LH receptor levels coincided with luteal maintenance in oestrogen-treated animals, although it is not certain that this was the cause of the prolongation of luteal activity. Maintenance of the corpora lutea is dependent on LH in the pig from about Day 14 after oestrus (du Mesnil du Buisson, 1966Buisson, , 1973Anderson et al, 1967;Spies, Slyter, & Quadri, 1967) and therefore it might be assumed that luteal function required LH during the period of oestrogen-stimulated progesterone secretion after Day 15. This would be consistent with the lack of effectiveness of oestrogens in maintaining luteal function after hypophysectomy (du Mesnil du Buisson, 1966) or pituitary stalk section (Anderson et al, 1967).…”

“…Maintenance of the corpora lutea is dependent on LH in the pig from about Day 14 after oestrus (du Mesnil du Buisson, 1966Buisson, , 1973Anderson et al, 1967;Spies, Slyter, & Quadri, 1967) and therefore it might be assumed that luteal function required LH during the period of oestrogen-stimulated progesterone secretion after Day 15. This would be consistent with the lack of effectiveness of oestrogens in maintaining luteal function after hypophysectomy (du Mesnil du Buisson, 1966) or pituitary stalk section (Anderson et al, 1967). However, the proportion of receptors occupied by LH, which presumably reflects the action of LH on the tissue (Suter et al, 1980), was reduced during the period of prolonged luteal function suggesting that the relationship between LH receptor level and luteal activity is complex.…”

“…Alternatively, the luteolytic effect of the uterus may be reduced by a rise in uterine blood flow, in response to administered oestrogen, leading to a drop in the concentration of PGF-2a in uterine venous blood by dilution (Ford, Christenson & Ford, 1982). However, there is evidence that a pituitary hormone may be involved in the luteotrophic action of oestrogens, since oestrogen alone fails to maintain corpora lutea after hypophysectomy or pituitary stalk section (du Mesnil du Buisson, 1966;Anderson, Dyck, Mori, Henricks & Melampy, 1967 (Lowry, Rosebrough, Farr & Randall, 1951 Occupied receptor concentrations were estimated by eluting endogenous LH from the luteal receptor preparations and measuring LH by radioimmunoassay. Preparations (2 ml) containing 30-50 mg protein were incubated overnight at 4°C in 6 ml of freshly prepared 1 N-formic acid, pH 2-4.…”

Cloning and expression of a unique short form of the porcine prolactin receptor

“…A vital role exists for PRL during reproduction in pigs as pituitary PRL is required to maintain the corpora lutea, and therefore gestation (Anderson et al 1967, Forsyth 1986. PRL also has a crucial role during mammary gland growth and lactation in this species (Farmer et al 1998, Farmer & Petitclerc 2003.…”