Involvement of Endogenous Proteolytic Activity in Thiol-Induced Release of DNA Template Restrictions in Rabbit Sperm Nuclei

Treatment of rabbit spermatozoa with Triton X-100 and dithiothreitol for increasing periods of time results in progressive increases in both the percentages of spermatozoa with swollen nuclei and in the ability of the swollen nuclei to serve as template for DNA synthesis. The involvement of endogenous proteolytic activity in this thiol-induced swelling and release of template restrictions is suggested by the fact that when spermatozoa are incubated in solutions containing various inhibitors of proteolysis (soybean trypsin inhibitor, lima bean trypsin inhibitor, or p-aminobenzamidine) in addition to Triton X-100 and dithiothreitol, inhibition of nuclear swelling and DNA template activity occur. The degree of inhibition is dependent upon the concentration of inhibitor employed. These results demonstrate a direct relationship between release of DNA template restrictions and nuclear swelling, and suggest that both processes depend upon some degree of endogenous proteolytic activity as well as upon disulfide reduction.