PRL action on E2 ovarian secretion

5 Amenorrhea hyperprolactinemic women in previous intermittent treatment with bromocryptine, received bromocryptine for three periods of 5, 4, 3 days; each treatment phase was followed by a ten days suspension. During treatment and during suspension FSH, LH, PRL and E2 were tested. There was no significative variation of FSH and LH; PRL lowered during treatment and reached basal values during suspension. Ovarian response (E2) varies with PRL levels. There was a statistically significative negative correlation between PRL and 17-beta-E2.     

Effects of bromocriptine mesylate on the composition of the mammary secretion in non-breast-feeding women.

A double-blind trial was performed on 26 women, who had elected not to breast-feed their infants, to determine the effect of bromocriptine mesylate (2.5 mg twice daily for 14 days postpartum) on the composition of the mammary secretion during lactogenesis. Mammary secretion (less than 5.0 ml) was collected from each breast of each woman at daily intervals during the 14-day treatment period and the progressive changes in the concentration of the milk constituents, lactose, alpha-lactalbumin, serum albumin, total protein, lactoferin, IgA, IgG, sodium and potassium were determined. The degree of milk leakage and breast engorgement were also assessed. Both the subjective assessments and the changes in the concentration of the milk constituents demonstrated that lactogenesis occurred between about Day 2 and Day 5 postpartum in the placebo group (in the absence of the suckling stimulus) but was suppressed in the bromocriptine-treated group.     

Inhibin and related peptides. Mechanisms of action and regulation of secretion

The structure of inhibin is known: it consists in a heterodimer constituted by one alpha and one beta subunits. The homodimer of beta A or the heterodimer beta A or the heterodimer beta A-beta B called activin A and B stimulates the release and the synthesis of FSH by gonadotrophs. Inhibin displays actions at hypophyseal, hypothalamic and gonadal levels. Produced by granulosa cells in female and by Sertoli cells in male, inhibin synthesis is stimulated by FSH, and reduced by hypophysectomy and progesterone. At the present time, there is no evidence for a signal from germinal cells to modify inhibin production. Inhibin secretion evolves with follicular maturation as aromatase activity whereas luteinization arrests its production. Nevertheless it seems to exist large difference in the regulation of inhibin secretion from one species to the other. Sperm inhibin levels are correlated with spermatozoa number. Its administration to the sheep induce either an anovulation or an increase of ovulation rate according to the scheme of treatment.     

Preferential mammary storage and secretion of immunoglobulin gamma (IgG) subclasses in swine.

Levels of three immunoglobulin gamma (IgG) subclasses, IgGA, IgGB and IgGC, were measured in sow sera, mammary glands, colostrum and milk samples by the single radial immunodiffusion. Serum IgGA and IgGB levels, but not IgGC, showed time dependent variations during gestation and lactation periods. The IgGA level started to decline at day 106 of gestation, reached its minimum at farrowing, and returned to the pre-gestation level 1-3 weeks after weaning. The serum IgGB level started to decrease at day 111 of gestation, reached its minimum at farrowing, and returned to the initial gestation level 1 week after farrowing. A notable decrease (P less than 0.1) in serum IgGC level was observed only on the day of farrowing. IgGA and IgGB were preferentially stored in mammary glands of full-term pregnant sows and secreted into colostrum after farrowing. In contrast, relatively small amounts of IgGC were stored in the mammary glands and secreted into colostrum. These data are interpreted as an indication that the preferential storage of IgGA and IgGB in the mammary gland of sows occurs at the time of significant decreases of these two IgG subclasses in the sera during late gestation and early lactation.     

Gestational changes in steroid hormone biosynthesis, secretion, metabolism, and action

This article examines the regulatory mechanisms and anatomic interrelationships governing pregnancy-related steroid hormones from conception through parturition.