Two dimensional SDS PAGE analysis of epididymal tissue proteins of normal and castrated bulls (Bos taurus) and identification of an androgen dependant protein

A study was undertaken with an objective of two dimensional SDS-PAGE analysis of protein profile in tissues of all caput, corpus and cauda of epididymis in both castrated and normal bulls and identification of androgen dependent protein/s in the epididymal tissues of bull (Bos taurus). Two dimensional SDS-PAGE analysis for protein spots of different molecular weight (MW) with pI 3.5 to 7.35 and pI > 7.35 to 9.3 between the three regions in the normal and castrated bull as well as between normal and castrated bull of a particular region revealed significant differences. Similarly, comparison between the three regions of the normal and castrated bull epididymis for the number of protein spots irrespective of the MW in pI range of 3.5 to 7.35 and pI range > 7.35 to 9.3 revealed significant differences. The number of protein spots found to be significantly higher in caput, corpus and cauda epididymis of the normal bull when compared to similar region of the castrated bull epididymis. Most of the proteins, which are secreted, are having MW between 20 and 85 kDa. Six proteins, which are known to be highly dependent on androgens, are also of acidic in nature except for one protein having basic pH. A protein spot (pI: 6.55–6.85, and MW: <20 kDa) which appeared at the same site in all the three regions of the epididymis in the normal bull but was absent at the same site in all the three regions of the castrated bull was subjected for identification of the protein by MALDI-MS. The results revealed that this protein is an interferon-stimulated protein and it could be ISG15/UCRP.