Effect of Protease Inhibitors onin VitroBreakdown of Uterine Histones from Hormone-Treated Rats

Abstract

Nuclei and chromatin were prepared from ovariectomized rats that had been untreated (U), treated with estradiol (E) or estradiol plus progesterone (EP). Aliquots were incubated at 0°C, 37°C or 37°C in the presence of protamine, leupeptin or antipain for 1 hr prior to extraction of histones. The histones were submitted to polyacrylamide gel electrophoresis and stained with dye. Incubation at 37°C resulted in degradation of the histones derived from E and EP rats. The 3 inhibitors when added to chromatin effectively prevented histone breakdown. On a milligram basis antipain and leupeptin inhibited histone breakdown when added to 37°C incubation of nuclei more effectively than when protamine was added. These findings suggest that leupeptin and antipain may be useful agents in biological systems where inhibition of trypsin-like proteolytic activity is desirable.