IMMUNOHISTOCHEMICAL STUDY OF ESTROGEN AND PROGESTERONE RECEPTORS IN DIFFERENT SIZE CLASSES OF OVARIAN FOLLICLES IN DROMEDARY CAMELS

Abstract

The present study aimed to investigate the normal distribution of estrogen (ERα) and progesterone (PR) receptors in the different classes of the ovarian follicles of the she-camel and their relation with the serum and follicular estrogen and progesterone hormonal level. Progesterone (P4) and 17β Estradiol (E2) serum levels, follicular estrogen receptors (Erα) and progesterone receptors (PR) expression and morphometry of different size classes of the ovarian follicles and corpus luteum during the estrous cycle in female dromedary camel were evaluated.The ERα and PR were detected using an indirect immunohistochemistry method (streptavidin-biotin immunoperoxidase method). Serum and follicular fluid were taken from 10 female dromedaries before and after slaughtering to evaluate the level of estrogen and progesterone in different size classes of the ovarian follicles (small >10mm, medium 10-15 and large <15 mm). Three cyclic non-lactating reproductively healthy she-camels were examined and bled daily to assess serum estrogen and progesterone levels during the follicular cycle and relate them to the size of the ovarian follicles and corpus luteum. The hormone levels were measured by radioimmunoassay. ERα was detected at low amounts in the follicular cells of the primordial, primary follicles and corpora lutea while, detected at moderate in the secondary follicles and high in the oocytes and in the tertiary follicles. On other hand, PR was detected in low reaction in secondary follicles and tertiary follicles. Moreover, it was estimated in a moderate reaction corpora lutea and corpora albicantia and stroma cells and in a strong reaction in the blood vessels. The number of cells expressing Erα and PR protein in ovarian cells was assessed by immunohistochemistry and computerized morphometric procedures. All data were analyzed with two way repeated measures ANOVA. Highest expression levels (p <0.01) of ER was found in the oolemma of the small and medium follicles but was absent in the granulosa cells surrounding these follicles. ERα was widely dispersed in the theca interna and theca externa of large tertiary follicles, it showed moderate staining intensity with homogeneous distribution in the cellular nucleus in theca interna and strong staining in the theca externa. The area and P4 serum concentration were higher during the luteal phase in R and C cows, as compared to F1. C and R animals displayed higher serum hormone levels than the F1 genotype, expression of mERα and glandular mPR and glandular sizes, which could pertain to the previously found better reproductive performance of C and R genotypes, probably as a result of their adaptation to a low-land tropical environmentExpression of PR was observed in stroma of all luteal structures but significantly stronger reaction was found in blood vessels of these structures. Estrogen concentration in both the follicular fluid (r=-0.06) and serum (r=-0.15) correlated negatively -but (not significantly)- with the size of the follicle while a positive non significant correlation was found between serum progesterone and the size of the corpus luteum. Serum and follicular fluid estrogen was higher in follicles exceeding 15 mm more than the lesser follicular categories. Slight difference in the concenttration of estrogen was found between follicles less than 10 mm in diameter and those between 10 – 15 mm. The expression of ER and PR and the secretion of their specific hormones in the ovary of she-camel were not always correlated with the presence of the hormones.