Prolactin and sexual maturation in the Japanese quail, Coturnix coturnix japonica

Effect of pregnant mare serum gonadotropin on plasma prolactin, luteinizing hormone, estradiol, and ovarian growth in incubating and out-of-lay turkeys

The effect of pregnant mare serum gonadotropin (PMSG) on ovarian growth and estradiol production was assessed in out-of-lay (OL) turkey hens that have low plasma concentrations of prolactin (PRL) and in incubating hens that have high plasma levels of PRL. In OL hens after injection with 400 or 2,000 IU PMSG, plasma concentration of PRL did not change, whereas ovarian weight and plasma concentration of estradiol increased by greater than 20-fold to levels comparable to those of laying hens. Follicles were not arranged in a hierarchy following the injection of either 400 or 2,000 IU PMSG into OL hens. There was a linear relationship between the dose of PMSG injected into incubating hens and the subsequent increase in plasma concentration of estradiol. Plasma levels of PRL were not different among hens injected with 0, 16, 80, or 400 IU PMSG, whereas plasma levels of PRL decreased in incubating hens injected with 2,000 IU PMSG. A significant increase in ovarian weight occurred only in hens injected with 2,000 IU PMSG. None of the hens deserted the nest following the injection of PMSG, indicating that the maintenance of incubation does not require a steroidogenically quiescent ovary. Although the regressed ovaries of both OL and incubating hens are responsive to gonadotropin stimulation, it would seem that the higher levels of PRL in incubating hens may act, in part, to suppress PMSG-induced ovarian growth and steroidogenesis.

Seasonal changes in some plasma hormones in pigeons from different environments

Seasonal variation in the plasma concentration of lutropin (LH), follitropin (FSH), prolactin (PRL), thyroxine (T4), triiodothyronine (T3) and corticosterone (B) were measured in the pigeon by RIA methods. Pigeons were maintained indoors under constant ambient temperature (Ta) and simulated natural daylight (LD), 12:12 L:D regimens or outdoors exposed to seasonal variations in temperature and photoperiod at Oulu, Finland. Only slight changes of gonadotropins (LH, FSH) were observed throughout the year, without any clear photosensitive or photorefractory period. In the indoor (natural LD) group, LH stayed elevated from May until October. Interdependence between the circannual hormonal fluctuation and photoperiod could not be shown, although the amplitude of FSH, T4 and T3 fluctuation of pigeons maintained in laboratory conditions were greater than that of natural LD and outdoor pigeons, whose circannual rhythms were similar. A high concentration of plasma PRL in autumn and the peak value of B in winter for all groups are thought to be correlated to lipid metabolism. Two peaks, the first in winter and the second in autumn, observed in T4 and T3 hormone profiles, may be due to molting of the pigeons.

Serum luteinizing hormone, progesterone, and estradiol levels in relation to broodiness in the turkey (Meleagris gallapavo)

Changes in nesting frequency, serum LH, progesterone, and estradiol were measured in relation to the onset of broodiness in turkeys. In each of two experiments the frequency of nest visits increased about four-fold in the 5 to 7 day interval before oviposition of the last egg associated with the onset of broodiness. In the 9 day period prior to oviposition of this egg LH levels declined from about 12 ng/ml to 6 to 7 ng/ml (Experiment 1) and from about 9 ng/ml to less than 5 ng/ml (Experiment 2). Progesterone levels declined during this same period going from about 2 to 2.5 ng/ml down to less than .5 ng/ml. In the 5 day period following the nadir in serum LH, which occurred on or a day or two after the last egg, levels of this hormone again rose substantially. Estradiol levels, assayed in Experiment 2, were generally low with many samples below detectability (less than 3 pg/ml). There were no consistent changes in serum estradiol until the day before oviposition of the last egg. On this day, and on the subsequent four days, mean estradiol levels were at a nadir (6 to 9 pg/ml) and rose to levels averaging over 11 pg/ml in the following five day period.

The effect of prolactin on reproductive function in female Japanese quail (Coturnix coturnix japonica)

The anti-gonadal or anti-gonadotropic actions of prolactin in Japanese quail (Coturnix coturnix japonica) were re-investigated. Treatment of mature regularly laying quail with 16 I.U. of ovine prolactin (NIH-P-S11) per day for 7 or 14 days caused significant (P less than .05) decreases in ovarian and oviductal weight and a reduction in egg production by the third day of treatment. The most frequent response to prolactin was complete cessation of ovulation for the duration of the experiment, but some birds showed no effects from the hormone treatment. Prolactin caused a significant (P less than 0.05) increase in body weight of the quail. Serum LH, measured during the expected time of the preovulatory LH surge, was significantly lower in birds treated with prolactin the day before sampling than in control birds. It was concluded that prolactin has a distinct anti-gonadal or anti-gonadotropic action in this species.