However, several other genes showed significant expression level changes in certain segments alone after either THP or DNB exposure. This indicates that THP and DNB cause significant changes in gene expression in specific compartments of the male reproductive system. For example, Psmb8 showed a P-value of 0.156 between the control and THP-treated animals when all four segments (i.e., the testis and the caput, corpus, and cauda epididymis) were analyzed together. However, according to the feed-segment interaction statistical analysis, the expression change of Psmb8 in the feed-segment interaction was statistically significant (P = 0.0047).
The subunit composition of the proteasomes may vary, and the 20S core can be found uncapped, capped with one 19S complex, capped with two 19S complexes, capped with an 11S activator complex, or capped with one 19S and one 11S complex (20S + 19S + 11S chimera). Given this variability and the paucity of knowledge about the significance of such varied proteasomal composition with regard to the testicular and epididymal function, we decided to focus our attention solely on the 20S proteasomal core. We chose to follow all three constitutive р-type subunits that can be substituted for by the inducible р subunits.