BIOLOGICAL-ACTIVITY IN THE REPOPULATING RAT SPERMATOCYTE AFTER THE WITHDRAWAL OF GOSSYPOL TREATMENT .4. THE ACTIVITY FOR THE MODIFICATION OF CORE HISTONES

Mature male rats were treated with gossypol for 8 weeks. Afterwards, t reatment was halted to allow the arrested spermatogonia to revive. Fif teen days after the withdrawal of the drug treatment, the repopulating pachytene spermatocyte (RPS) had a lower level of core histone H-3 an d H-4 acetylation (40 and 55% reduction, respectively) than that of th e control pachytene spermatocyte (CPS). The reduction in core histone acetylation was found in histone H-3 and H-4 but not in HA and H2B. Fo rty-five days after the withdrawal of the drug treatment, the inhibito ry effect on core histone acetylation was recovered. Both dot-blot and standard liquid assays were used to detect the nuclear histone acetyl ase activity in RPS and CPS. Fifteen days after the withdrawal of goss ypol treatment, the acetylase type A activity in RPS was reduced by 42 % when compared to CPS. It has been concluded that after gossypol trea tment, the activity for nucleosomal core histones acetylation was sele ctively inhibited. This effect is related to an inhibitory effect on t he histone acetylase activity.