[Biochemical studies on hypotrophy and hypoplasia in the post partum uterus of the rat (author's transl)].

In post partum rat uteri, the wet weight, the soluble protein and the DNA content were measured for ten days following delivery. After a lag period of 48 h, the weight and protein content of whole uteri decreased in parallel to one twelfth of the initial values. The DNA content did not change significantly. Hypoplasia contributed not more than 20% to the weight loss, so that at least 80% of the loss was due to hypotrophy. The protein content per cell nucleus (mg protein/mg DNA) decreased by 85% within 10 days. In non-pregnant control animals, uterus weight and protein content per cell nucleus were greater than those of animals measured on the tenth post partum day. In contrast, the protein concentration of the tissue (mg protein/g wet weight) was lower in the control group. It is suggested that this hyperinvolution is caused by the low estrogen levels of the lactating animals.