Simultaneous determinations of unconjugated estradiol (E2), estriol (E3) and 15 alpha-hydroxyestriol (E4) levels in maternal serum were studied serially to ascertain the significance of these estrogens in the feto-placental unit. The samples of serum were collected serially from 25 normal and 44 abnormal pregnancies. In normal pregnancy, these estrogen levels increased throughout pregnancy, especially E3 and E4 nearing the term. In 15 cases of IUGR pregnancy (including 4 cases of perinatal death), E2 levels were mostly low (less than M -- S.D.), E3 was within normal limits (M +/- S.D.) or low, and E4 was either high (greater than M + S.D.) or relatively low, and normal. In 9 cases of twin pregnancy, most E2 levels were within normal limits, while E3 and E4 were remarkedly high. The results signified that E2 indicated placental function, that E3 indicated placental and fetal function, and that E4 indicated fetal function.

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Adult female Wistar rats (in 12 hr light/12 hr dark) were pinealectomized (PX) or sham-operated (SO) either 21 days after ovariectomy or on the 15-17th day of pregnancy.Ovariectomized (OVX) rats were injected with estrogen and progesterone (EP) 48 hr before decapitation. Melatonin, serotonin or arginine vasotocin (AVT; 50, 100 or 200µg) were administered intravenously into OVX-EP rats 9 days after pineal removal.In PX and SO groups, the same study was done 3 days after delivery.Sera and pituitaries were collected 30 min after injection in order to determine prolactin (PRL) levels. Fifty µg melatonin significantly suppressed serum PRL levels in PX-OVX-EP rats and PX postpartum rats, but had not significant effect in SO-OVX-EP or PX postpartum rats. After administration of AVT, serum PRL levels markedly rose in PX and SO rats. These results suggest that melatonin may act not only to stimulate but also to inhibit rat PRL secretion and that the stimulatory function would be superior to its inhibitory function when the pineal gland is intact, prolactin; pineal gland; melatonin; serotonin; arginine vasotocin In mammals pituitary prolactin (PRL) secretion is regulated by stimulatory and inhibitory mechanisms. The pineal gland is usually considered to stimulate PRL secretion, because decrements of circulating PRL have been observed in pinealectomized (PX) rats (Donofrio and Reiter 1972;Relkin 1972;Ronnekleive and MacCann 1975), and because administration of pineal extract (Moskowska 1967) or pineal substances (Kamberi et al. 1971;Kuew-Husing and Meites 1973;Pavel et al. 1975) stimulates PRL secretion. We have previously reported that pinealectomy lowered serum PRL levels in ovariectomized (OVX) female rats treated with estrogen and progesterone (Takahashi et al. 1978). On the contrary,

Wistar female rats housed under conditions of 12 hr dark/12 hr light were pinealectomized (PX) or underwent sham-operation (SO) 21 days after ovariectomy, on the 7th or on the 15-17 th day of pregnancy. Serum and pituitary prolactin (PRL) levels in ovariectomized (OVX) rats were determined 9 days after pinealectomy. In the case of OVX rats receiving estrogen and progesterone injections (OVX-EP), PRL levels were determined 48 hr after injection administered 7 day after pinealectomy. PRL levels in pregnant rats were determined on the 20th day of pregnancy and in postpartum rats, on the 3rd day following parturition. As compared with the SO control, pinealectomy resulted in a significant decrease in the serum PRL level in the OVX-EP rats but in a significant increase in that level in the OVX, pregnant and postpartum rats. In OVX-EP rats, exogenous estrogen raised the serum PRL level less in PX than in SO rats, probably because the pineal gland is closely related to the facilitation of PRL secretion by estrogen. The high estrogen level in OVX-EP rats seemed to trigger pineal stimulation of PRL release, but low estrogen levels in OVX and postpartum rats or markedly high levels of progesterone in pregnant rats on the 20th day are thought to cause pineal inhibition.prolactin ; pineal gland ; estrogen ; progesterone There have been no uniform conclusions about the role of the pineal gland in pituitary prolactin (PRL) secretion in the rat, because different experimental conditions have resulted in either inhibition or facilitation of PRL release by the pineal gland. We have previously studied the change in PRL secretion after pineal removal and administration of pineal bioactive substances, such as melatonin, serotonin and arginine vasotocin (AVT) and have demonstrated that antagonistic mechanisms of the pineal gland which affect pituitary PRL secretion

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