The role of polyamines in growth factor induced DNA synthesis in cultured rat hepatocytes

BACKGROUND/AIMS: Hepatocyte growth factor and transforming growth factor-a are growth factors with important roles in hepatocyte proliferation. The po lyamines, putrescine, spermidine, and spermine are widely distributed in ma ny different cells and play an essential role in cell growth and differenti ation. The present study examined the role of polyamine in this growth prom oting factor-induced hepatocyte proliferation, in primary cultured rat hepa tocytes. METHODOLOGY: Hepatocytes were isolated from rats by the collagenase perfusi on method. Ornithine decarboxylase and S-adenosylmethionine decarboxylase a ctivities were measured as the release of (CO2)-C-14 from L-1[C-14]ornithin e and S-adenosyl-L-[carboxyl(14)C]methionine, respectively. The concentrati on of polyamine was analyzed by high performance liquid chromatography. RESULTS: When transforming growth factor-alpha and hepatocyte growth factor were added to the hepatocyte culture simultaneously, ornithine decarboxyla se activity, S-adenosylmethionine decarboxylase activity, polyamine concent ration and DNA synthesis increased additively. The increase in DNA synthesi s caused by transforming growth factor-alpha, hepatocyte growth factor, or both was completely inhibited by alpha-difluoromethylornithine and methylgl yoxal bis(guanylhydrazone). The inhibition was reversed by exogenous spermi dine or spermine, but not by putrescine. CONCLUSIONS: Increased spermidine or spermine levels are essential for hepa tocyte proliferation in cultured rat hepatocytes.