Specific inhibition of the incorporation of tritiated thymidine in regenerating rat liver by a rat hepatocytes supernatant.

Studies on endogenous inhibitors obtained from supernatant fluids of rat hepatocytes indicated that the supernatant arrests the normal cell cycle at two points, namely, before the beginning of the S phase and at the onset of metaphase when assayed in regenerating liver cells in situ. The specificity of this (these) inhibitory substance(s) was evidenced by the finding that no inhibition of cell division was observed in situ in tongue, intestine, or kidneys of animals injected with concentrations of the hepatocyte supernatant that inhibited cell division in regenerating liver. When higher concentrations of the inhibitor-containing supernatant were used, only the tongue epithelial cells were affected in addition to the regenerating liver cells.