DNA activity in the endometrial stroma of the cycling rat as measured by Feulgen staining and by [3H]thymidine incorporation.

By using cytophotometry, Fautrez (1966) and his colleagues have shown in a variety of hormonal receptors (i.e. thyroid, adrenals, ovary and vagina) that specific stimulation leads to an increase of Feulgen-measured DNA within the nuclei of target cells. According to these authors, this phenomenon is not necessarily related to an enhanced mitotic rate but would witness to a hormonedependent metabolic activity. As similar data were obtained in the uterus ofspayed mice (Leroy, Manavian & Hubinont, 1967) and rats (Leroy & Manavian, 1969), the present work was undertaken in order to verify if this concept is applicable to the endometrial stroma during the oestrous cycle. The oestrous cycles of groups of four animals (Wistar strain) were followed by daily vaginal smears and animals were killed around mid-day at various moments of the cycle (i.e. pro-oestrus, early and late oestrus and early and late di-oestrus). Sections of the uteri were homogeneously Feulgen-stained. The relative Feulgen-DNA content was determined with the Lison histophotometer (Lison, 1950) in about 100 stromal nuclei per uterus. The results obtained in groups of animals were pooled and statistically analysed according to the large samples method described by Snedecor (1956). As the observed values showed