[Study of the biological activity of chalones isolated from normal and regenerating liver].

In contrast to the extract derived from the normal rat liver, the chalone-containing extract from the regenerating liver did not inhibit hepatocyte division in the in-vivo test system 22 hours or 28 days after partial hepatectomy. The regenerating liver extract reduced by 55% the level of DNA synthesis by hepatocytes 28 days after hepatectomy. The testing of biological activity of individual protein fractions of the chalone-containing extract from the regenerating rat liver which were separated by preparative slab gel electrophoresis revealed (28 days after hepatectomy) the coexistence in the extract of both stimulant of hepatocyte mitosis and inhibitor of DNA synthesis. It is assumed that the lack of the inhibitory effect in the chalone-containing extracts from the regenerating liver might be related to the competitive interconnections between the inhibitors and stimulants of mitosis rather than to the loss of the tissue-specific inhibitor.