Unscheduled DMA Synthesis Induced by Procarcinogens in Suspensions and Primary Cultures of Hepatocytes on Collagen Membranes1

Unscheduled DMA synthesis was induced by procarcinogens in freshly isolated suspensions and primary cul tures (6 days old) of hepatocytes on collagen membranes. Incorporation of ['HJthymidine in the presence of hydroxyurea was used to measure unscheduled DMA synthesis. When hepatocellular DNA was isolated on cesium chlo ride gradients, significant levels of unscheduled DNA synthesis were measured. Similar concentrations of procarcinogens elicited higher levels of unscheduled DNA synthesis in hepatocellular suspensions than in primary cultures. The results demonstrate that hepatocytes cul tured on collagen membranes can metabolize chemical carcinogens. Suspensions of freshly isolated hepato cytes, however, are more active in procarcinogen metab olism than are those of primary cultures. The selective advantages of the two systems of hepatocytes can be utilized for the establishment of short-term in vitro screen ing systems of mutagens and carcinogens.