Changes in expression of estrogen receptor alpha (ER) mRNA were studied in special reference to follicular growth of the ovarian follicles in laying quail. Levels of mRNA were determined by RT-PCR in the ovarian stroma, each class of the ovarian follicles, oviductal parts and in the liver. Low levels of ER mRNA were detected in stroma, the small white follicles, large white follicles and small yellow follicles and in the theca layer of the three largest preovulatoy follicles. Although the level in the granulosa layer of the F3 was also low, the level significantly increased in F2 and F1. Relatively higher levels were found in the liver and oviduct, and that in the magnum was the highest among all tissues examined. The level in the F1 granulosa layer was comparable to that in the liver which actively synthesises egg yolk proteins for the sake of estrogen and ER. The results of the present study demonstrate that (1) ER mRNA is present in each compartment of the reproductive tissue in quail, (2) the marked expression of ER mRNA in the granulosa layer of the largest follicle may indicate the involvement of estrogens in the biosynthesis of inhibin/activin, progesterone and yolk perivitelline layer protein, (3) very high expression of ER in the oviductal tissues may be related to the role of estrogens in cell proliferation and protein synthesis in the oviduct.
The purpose of the present study was: (1) to demonstrate immunocytochemically the localization of histamine in the wall of four chicken oviductal parts, i. e. infundibulum, magnum, isthmus, and shell gland, (2) to identify the presence of mast cells in chicken oviduct, and (3) to determine histamine concentration in oviductal tissue by the spectrofluorometric method. Experiments were carried out on Isa Brown laying hens decapitated just after oviposition. The specific immuno-reactivity for histamine and the presence of mast cells were found in the wall of all the examined oviductal parts. The immuno-reactive histamine was localized in epithelium, tubular glands, connective tissue layer, circular and longitudinal muscles, and endothelium and muscles of blood vessels. The intensity of immuno-positive reaction was as follows: infundibulum > shell gland > magnum = isthmus and correlated with quantitatively determined histamine level and tissue density of mast cells. It is suggested that mast cells are the main source of histamine in the chicken oviduct.
The role of estrogens in hen reproduction is well established. However, the distribution of estrogen receptors in the chicken ovary is unknown. Therefore, the mRNA expression of alpha (ERalpha) and beta (ERbeta) estrogen receptors was examined within the ovaries of laying hens. Expression of ERs was determined by RT-PCR analysis. The presence of ERalpha and ERbeta mRNAs was found in the ovarian stroma and white, yellowish, small yellow and the largest preovulatory (F3-F1) follicles. ERalpha and ERbeta mRNAs were detected in the granulosa and theca layers of the walls of preovulatory follicles. The expression of ERalpha mRNA was markedly higher than ER? mRNA in all examined ovarian compartments. Within the ovary, the relative expression of both ER mRNAs depends on the follicular diameter and the layer of the follicular wall. The results demonstrate the expression of both ERalpha mRNA and ERbeta mRNA in all compartments of the chicken ovary, suggesting different pathways of estrogen action in the avian ovary. Much higher expression of ERalpha mRNA indicates that this form of estrogen receptor is predominant in the chicken ovary. The clarification of the mechanism of ER? and ER? participation in the ovarian functions of birds necessitates further experiments examining ERs at the protein level.
The concentrations of ovarian steroids (estradiol ? E2, progesterone ? P4 and testosterone ? T) and thyroid hormones (thyroxine ? T4 and triiodothyronine ? T3) were determined in blood plasma of the domestic hen during sexual maturation and the initial period of egg lay. Blood samples were collected from Hy-Line pullets at 3 day intervals from days 87 to 144 day of life, i.e. 42 days before and 14 days after the onset of egg lay (OEL). Ovarian and thyroid hormones were measured by RIA methods. During sexual maturation an increase in ovarian steroids in the blood plasma was observed. The maximum E2 and P4 levels were recorded on day 6 and day 3 prior to OEL, respectively. In the case of plasma T level, an increase from 42 to 18 days before OEL followed by a decrease and a renewed increase from day 9 till OEL was observed. The relatively unchanged plasma level of T4 until day 9 before OEL decreased significantly just before the first oviposition while the T3 level gradually decreased between day 42 and day 9 before OEL, and then increased and again decreased from day 3 before till day 3 after OEL. During sexual maturation the following statistically significant coefficients of correlation between ovarian steroids and T3 were found: E2 vs. T3 ? r = -0.551 and P4 vs. T3 ? r = -0.373. There was no significant correlation between T and T3 or between the examined steroids and T4. The data obtained indicate that during sexual maturation of the domestic hen there is a negative relationship between the ovary and the thyroid gland.
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