Alternate fluctuations of leucine and thymidine incorporation by mammary tumors in rats during the estrous cycle.

tissue mitotic counts, which also peaked at diestrus 1. Radioactivities in the acid-soluble fraction of the incubated tissues were not significantly different for either labeled precursors throughout the estrous cycle. Autoradiographic studies of tissues collected after incubation with [3H]thymidine showed that silver grains were localized over cell nuclei. The data indicate that the growth of 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats during the estrous cycle is associated with a peak of [3H]leucine incorporation at proestrus and a wave of [3H]thymidine incorporation during metestrus-diestrus.