Prolactin administration during the luteal and follicular phase of the oestrous cycle of gilts

Abstract

Summary. In Exp. I infusions of prolactin (0\m=.\5mg in 2 ml sterile saline) were repeated every 2 h for 36 h on Days 12\p=n-\13of the cycle. In Exp. II infusions of prolactin were administered from Days 17 to 19 (60 h) at 2-h intervals. Control gilts were given 2 ml sterile saline at similar intervals during the same period. Basal prolactin concentrations before initiation of infusions ranged from 1\m=.\3\ m=+-\0\m=.\1to 5\m=.\6\ m=+-\ 2\m=.\2 ng/ml in both experiments. By 5 min after a prolactin infusion, mean plasma prolactin concentration ranged from 74\m=.\9\ m=+-\5\m=.\8to 113\m=.\0\ m=+-\ 9\m=.\5ng/ml, but then declined to \ m=si meq\ 10 ng/ml just before the next infusion of prolactin. Administration of prolactin during the luteal phase of the oestrous cycle of the gilts had no effect on basal levels of progesterone, oestradiol or LH. During the follicular phase there were no differences (P >0\m=.\05) between control and prolactin-treated gilt progesterone and LH concentrations, but oestradiol plasma values were decreased (P <0\m=.\05) on the 2nd and 3rd day of prolactin treatment. Our results would indicate that prolactin does not play a major role in the regulation of the oestrous cycle of the pig.

Hypogonadism in Heat Stressed Goats: Poor Responsiveness of the Ovary to the Pulsatile LH Stimulation Induced by Hourly Injections of a Small Dose of GnRH.

“…Prolactin is known to increase several times under hot environmental conditions [16,26] and it has been shown that prolactin inhibits the ovarian aromatase activity and thereby suppresses estradiol secretion [27][28][29]. The induction of hyperprolactinemia either by prolactin injection in sows [30] or TRH injection in ewes [31] reduces estradiol secretion with little change in LH and FSH secretion in the ewe. On the other hand, it has been shown that administration of ACTH during the follicular phase results in a decrease in estradiol secretion and a delay in the preovulatory LH surge in cows [32].…”

Role of prolactin in the regulation of ovarian function in pigs

“…However, in-vivo studies (Dusza et at, 1986; L. Dusza, R. Ciereszko, G. Kotwica & S. Okrasa, unpublished) involving prolactin administration to intact gilts (Fig. 2) and sows (Figs 3, 4) during the follicular phase of the cycle showed that the increase in plasma prolactin concentration (to about 100 ng/ml in gilts and to about 45 ng/ml in sows) had no effect on peripheral progesterone concentrations.…”

“…It has also been observed that high concentrations of prolactin suppressed ovarian oestradiol-170 and oestrone secretion in pigs. Dusza al. (1986) reported that prolactin administration for 60 h during the follicular phase of the oestrous cycle in intact gilts (Fig.…”

Luteolysis in the pig: studies into the mechanism of action of prostaglandin F2[alpha]

“…More recently, Dusza et al (1986) administered prolactin to gilts on day 12 and 13 of the estrous cycle and observed no change in plasma progesterone concentrations when compared to saline injected control gilts. In vitro studies demonstrated no effect of prolactin on progesterone production by porcine luteal cells isolated from corpora lutea obtained on days 5-13 of the estrous cycle (Gregoraszczuk, 1983;Przala et al, 1984).…”