G₂ Sub‐Population In Mouse Liver Induced Into Mitosis By Lead Acetate

Abstract

ABSTRACT A single intracardiac dose of lead acetate (40 μ lead/g body weight) induced a 25‐fold increase in mitosis of mouse hepatocytes 5 hr after injection, as determined by autoradiography. the prompt appearance of a mitotic wave and the relatively large number of mitoses suggest that the mitotic cells were derived from a hepatocyte sub‐population arrested in the G 2 phase. the injection of lead also stimulated a small increase in labeled hepatocytes within 6 hr. Analysis of grain counts gave no evidence for unscheduled DNA synthesis. the incremental labeled cells may have originated from a small fraction of the G 1 population that was ready to enter the S phase without the usual pre‐synthetic delay.