ALTERATIONS IN CONCENTRATIONS OF INHIBIN IN RELATION TO FSH AND STEROIDS HORMONE DURING ESTROUS CYCLE IN EGYPTIAN BUFFALOES

Abstract

Seven Egyptian buffaloes were used to study the plasma changes of inhibin, FSH, estradiol-17b and progesterone concentrations during the at estrous cycle. These hormones were determined at estrous and two interval until day twenty two of estrous cycle. Plasma inhibin estimated by enzyme-linked immunoasorbent assay (ELISA). Both FSH, estradiol-17β and progesterone were estimated by radioimmunoassay (RIA). In order to elucidiate the feedback system controlling mentioned hormones during estrous cycle, variations in the levels of hormones and their inter-relationshpis were studied. Plasma inhibin levels ranged between 439.28 and 584 pg/ml during various stages of estrous cycle, peak of inhibin level was at day of estrous by an average of 584 pg/ml. Follicle stimulating hormone levels were higher at day of estrous (25.48 ng/ml), decreased and fluctuated towards end of estrous cycle and then increased at twenty two days of estrous cycle. Peak of estradiol-17β was 18.54 pg/ml at day of estrous, while the peak of progesterone was 4.39 ng/ml at twelfth day from the start of estrous. It could be concluded that each of inhibin and estradiol-17b seems to have a feedback regulatory effect on FSH secretion in buffaloes. Key words: Inhibin, FSH, estradiol-17b, progesterone, estrous cycle, buffalo.