Peripheral effects of prolactin in reproductive function. II. Female reproductive function

: Prolactin (PRL) has an important peripheral role to play in female reproductive function. This hormone, in physiological concentrations, is necessary so that the follicle can mature properly. It also helps the maturation of oocytes and is essential for the physiological action of the corpus luteum so that progesterone production can be stimulated. It inhibits its catabolism and is responsible for keeping up the numbers of LH and oestradiol receptors. It works through the intermediary of prolactin receptors which are localised on the granulosa cells. The mechanism is through immuno-cytochemistry and it can be distinguished biochemically (Ka = 0.5 10(10) M). Probably, when levels are high it upsets follicular maturation by inhibiting the biosynthesis of the oestrogens and also by stimulating the secretion in the granulosa cells of a substance that inhibits oocyte maturation: and prolactin exercises a luteolytic action by stimulating the catabolism of the hormone and lessening the numbers of LH receptors. On the other and, there are high concentrations of PRL in amniotic fluid. As endometrial cells undergo the phenomenon of decidualization they produce PRL which is identical biochemically with the pituitary hormone. Certain steroids seem to regulate this synthesis of PRL. This hormone must play a role in fetal osmoregulation through the intermediary of prolactin receptors.