Proliferation related peptides in quiescent and regenerating rat liver.

Aqueous extracts of resting (C) and 30 h regenerating (P) rat livers were partially purified by a combination of ion exchange-, Sephadex- and paper chromatographic techniques. It was demonstrated that a limited number of the semipurified chromatographic fractions inhibited or stimulated both DNA synthesis and cell proliferation, the effect being partially determined by C or P liver origin of the fractions. It was also shown that biological activities were mediated by hepatic peptides of middle molecular size in the semipurified fractions. It is suggested that regulation of hepatocyte proliferation might be under a dual control operating through an interplay of stimulatory and inhibitory peptides, the final outcome determined by their interaction.