Antipain and leupeptin restrict uterine DNA synthesis and function in mice

As in rats, administration of estradiol to ovariectomized mice results in a trypsin-like proteolytic activity in the uterus. After fractionation of uteri from estradiol-treated ovariectomized mice the protease activity was found in the 12,000 times g pellet and the nucleus, appearing first in the former. Further fractionation of the pellet by discontinuous sucrose gradient centrigugation resulted in sedimentation of the protease with 5'-nucleotidase, a marker enzyme for plasma membrane and separate from mitochondrial and lysosomal enzyme markers. Solubilization was best accomplished by lysis at 37 degrees. The soluble enzyme from mouse uterus had optimal activity at about 43 degrees and pH 8.3 and was inhibited by diisopropylfluorophosphate, tosylarginine methyl ester, antipain, and leupeptin, but not by soybean trypsin inhibitor. Inhibition in vitro by antipain and leupeptin, two low molecular weight peptides, prompted the study of their effect in vivo on the mouse uterus. After intact, cycling female mice received subcutaneous injections of antipain and leupeptin for 16 days, their uteri showed significant diminution in weight and total DNA when compared to untreated controls. Fertility rates were also diminished. Trypsin-like protease activity may be essential to normal uterine metabolism and function.