Keeping in view the significance of role of epididymis in sperm maturation in mammals, the histomorphology and biochemical composition of its three regions; proximal caput, middle corpus and distal cauda were studied in the house rat, Rattus rattus, a species of great economic importance being a commensal rodent pest. Histomorphological observations revealed the presence of rounded and oblong tubules filled with spermatozoa in all the regions of epididymis. The tubular as well as luminal diameter and the thickness of epithelial lining was highest in caput as compared to that in corpus and cauda indicating the more secretory activity in this region. The sperm motility and concentration were significantly higher in cauda as compared to that in caput and corpus. The level of biochemical constituents including proteins, lipids, phospholipids, cholesterol, free fatty acids and sialic acids estimated in tissues of three epididymal regions, their fluids (only proteins) and spermatozoa progressively decreased from caput to corpus and to cauda epididymal tissues while their concentration successively increased in the spermatozoa from caput to corpus and to cauda epididymii. In epididymal fluid, protein content significantly increased from caput to corpus and to cauda. It reveals that maximum secretory activity was in the caput region of epididymis and content of various biomolecules was highest in the spermatozoa collected from cauda epididymis perhaps of its being their storage organ.
Keywords: Epididymis, Rattus rattus, histomorphology, biochemical composition.