EFFECT OF AN INHIBITING FACTOR ISOLATED FROM RAT LIVER ON DNA POLYMERASES IN REGENERATING RAT LIVER |
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Authors: | G. Pietu N. Munsch S. Mousset C. Frayssinet |
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Affiliation: | U17 de l'INSERM, Hospital P. Brousse;Institut de Recherches Scientifiques sur le Cancer, Villejuif, France |
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Abstract: | We partially purified an inhibitory factor (LIF), isolated from 105,000 g supernatant of a saline adult rat liver homogenate. LIF stopped in vitro cell multiplication by blocking the G1—S transition, and reduced in vivo [3H]thymidine incorporation into liver DNA in two-thirds hepatectomized rats. This reduction in DNA synthesis was observed at 24 hr after hepatectomy, even when the LIF was injected before the beginning of the S phase, 10 hr after hepatectomy, i.e. when DNA polymerase activity had not yet increased. Under these experimental conditions, LIF in vivo treatment prevented α DNA polymerase activity from increasing after partial hepatectomy, so that enzyme activity at 24 hr in LIF-treated rats decreased compared to the controls. No direct inhibitory effect of LIF on α DNA polymerase was detected. LIF did not affect β DNA polymerase. These results suggest that LIF plays a part in controlling liver growth. |
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