Inter and intra diurnal variations of DNA, RNA and protein synthetic activity in newborn, infant and young adult mouse livers.

The present report is a continuation of our previous studies on the observations of macromolecule precursors incorporated into the liver of newborn (1-10 days), infant (11-21 days) and young adult (41-50 days) old mice C57BLfemale X C3Hmale Fl and 3-hour interval circadian rhythm in livers of 15 day-old mice. 3H thymidine, 3H uridine and 3H leucine were used for studying incorporation into the macromolecules. DNA, RNA and protein were prepared by a modified Kirby's procedure. The data obtained indicate fluctuation of DNA activity approximately at 5-day intervals with a decreasing tendency up to 50 days of age. In 15-day-old mice, the peak of synthetic DNA activity was observed at 9.00 a.m. and the lowest values were found the next day at 6.00 a.m. Our results should provide fundamental data from which it would be possible to speculate whether the hepatocarcinogenic effect of different compounds with or without a special affinity to induce hepatoma may be correlated to different macromolecular synthetic activity.