Changes in uterine protein secretion during luteal and follicular phases and detection of phosphatases during luteal phase of estrous cycle in buffaloes (Bubalus bubalis)

Changes in uterine proteins during different reproductive states and their functional significance though known in other species have not been established in buffaloes. An attempt has been made to unravel the changes in composition of buffalo uterine secretion with growth and regression of corpora-lutea during early, mid and late luteal and follicular phase of estrous cycle using gel filtration and electrophoresis techniques. Also the phosphatases activities in luteal phase uterine secretions have been studied. Gel filtration chromatography analysis revealed a protein peak in void volume of the column, the intensity of which was more in all the luteal phase samples than follicular phase samples. Alkaline phosphatase was also found eluted in the void volume. The other three uterus-specific peaks (Peaks V-VII) were detected below 13.7 kd molecular weight. There were at least five peaks of acid phosphatases activity in chromatogram. Silver staining of SDS-PAGE gel detected as many as 40 protein bands in the uterine fluid of which nine proteins were glycoproteins. Molecular weight (MW) comparison revealed the major protein band at 66 kd which could be serum albumin. Comparison of uterine proteins with serum protein bands revealed a 93.5 kd glycoprotein in buffalo serum that did not appear in uterine fluid and at least 11 uterus-specific protein bands (506, 470, 241, 114, 49, 38, 33, 26, 19.2, 16, and 14.3 kd). The 38 and 19.2 kd bands were luteal-stage specific. Intense periodic acid Schiff's (PAS) stained bands in uterine proteins compared to serum indicated glycosylation process in endometrial epithelial cells. The study suggested that buffalo uterine secretion contained mainly serum and several uterus-specific proteins of which few were luteal phase specific. Further study on characterizing the unique or most abundant proteins and defining their role in uterine functions would help to address the cause of low reproduction rate in buffaloes.