Increased spermidine or spermine level is essential for hepatocyte growth factor-induced DNA synthesis in cultured rat hepatocytes

Background/Aims: Hepatocyte growth factor is a potent mitogen for mature hepatocytes and seems to act as a trigger for liver regeneration. Hepatocyte growth factor was first purified from human and rabbit plasma and rat platelets. Additionally, putrescine, spermidine, and spermine are widely distributed in many different cells; intracellular concentrations of these polyamines are closely related to cell proliferation. The present study examined whether polyamine metabolism is involved in hepatocyte growth factor-induced DNA synthesis in primary cultured rat hepatocytes. Methods: Hepatocytes were isolated from rats by the collagenase perfusion method. Ornithine decarboxylase and S-aden-osylmethionine decarboxylase activities were measured as the release of 14CO2 from l-[1-14C]ornithine and S-adenosyl-l-[carboxyl-14C]methionine, respectively. Results: α-Difluoromethylornithine inhibited hepatocyte growth factor-induced DNA synthesis by only 21%. On the other hand, methylglyoxal bis(guanylhydra-zone) completely inhibited hepatocyte growth factor-induced DNA synthesis to nontreated control level. The inhibitory effect of methylglyoxal bis(guanylhydrazone) on hepatocyte growth factor-induced DNA synthesis was reversed by exogenously added spermidine or spermine. Conclusions: Spermidine or spermine is essential for hepatocyte growth factor-induced DNA synthesis in primary cultured rat hepatocytes.