Abstract
Intraperitoneal administration of actinomycin D resulted in inhibition of estrogen-stimulated uterine weight in immature mice. Estrogen-stimulated uterine carbonic anhydrase activity was inhibited to a much lesser degree than uterine weight. Alkaline phosphatase activity appears to be even more stable. In experiments of 48-hr. duration, actinomycin had to be injected 4 hr. before estradiol in order to achieve inhibition of carbonic anhydrase activity. Inanition can play an important role in the interpretation of these experiments.