Biological activity in the repopulating rat spermatocyte after the withdrawal of gossypol treatment: II. The activity for the synthesis of cellular and nuclear basic proteins.

The synthesis of cellular and nuclear basic proteins in the first generation of the repopulated pachytene spermatocyte (RPS) and the control pachytene spermatocyte (CPS) was studied by the incorporation of 3H-arginine into proteins. After pretreatment with gossypol for various lengths of time, the synthetic activity for cellular protein in the RPS was slightly inhibited. In comparison to CPS, on the other hand, the inhibition ranged from 12% to 26% (for gossypol pretreatment from 3 to 12 weeks, respectively). However, the synthetic activity for nuclear basic protein in the RPS was drastically reduced in comparison to that of the CPS. The reduction ranged from 46% to 61% in RPS after receiving gossypol pretreatment for 3 to 12 weeks, respectively. Gel electrophoretic separation of the basic protein extracted from the pachytene cell indicated that the major basic proteins are nucleosomal linker and core proteins, i.e., histone H1, H2A,B, H3, and H4, and with a lesser amount of sperm-specific BP and X1 proteins. After gossypol treatment in the RPS, the synthesis of sperm-specific proteins (BP and X1) and core histones (H2A and H4) became drastically reduced. Finally, the effect of gossypol on the ratio of nuclear basic protein to DNA in RPS and the direct correlation of this ratio to nucleosomal spacing and chromatin structure are discussed.