A period of appearance of NADH-diaphorase activity in mitotic cycle of Ehrlich's ascites tumor cells.

NADH-diaphorase, one of flavoenzymes, is known to lose scarcely its activity in riboflavin deficiency. In that case, as reported previously (1), the enzyme still has its activity even in the intestinal mucosa, a very actively regenerating tissue. We therefore assumed that this enzyme increased its activity directly before mitosis. In order to confirm this assumption we have studied the activity of the enzyme in the skin (2), regenerating liver (3), yeast cells (4) and Ehrlich's ascites tumor cells (5, 6). The most important basis for the assumption is the finding that in Ehrlich's ascites tumor cells, no NADH-diaphorase activity was detected when the cells are in interphase, whereas a strong activity was found only when the cells were con sidered to be near prophase. However, we felt many difficulties under ordinary microscope to decide that the cells were in the stage of prophase. Furthermore, it was almost impossible to decide that the cells were in antephase. We therefore described in the previous paper (7) that NADH-diaphorase activity began to appear near prophase including the possibility of the appearance of the enzyme activity in antephase. In the present study we followed the course dynamically by tracing the rela tionship between the appearance of NADH-diaphorase activity and the nuclear incorporation of thymidine-H3 by means of autoradiography and histochemistry. EXPERIMENTAL DDN male mice were used on the 8th day of intraperioneal inoculation of Ehrlich's ascites tumor cells. 1. Administration of Thymidine-H3 The ascitic fluid was obtained 2, 5 , 8, 11, 14, 17 and 20 hours after intraperi toneal injection of 0 .3 ml (250ƒÊc) of thymidine-H3 (specific activity, 5.0c/mmole).