ISOLATION AND CHARACTERIZATION OF A GROWTH-INHIBITORY FACTOR FROM HAMSTER LIVER

Among lysates from various organs and tissues of adult hamsters only l ysates from liver demonstrated an inhibitory effect on the cell growth of SV40-transformed hamster fibroblasts in culture. Lysates from the liver of fetal hamsters and those from 7-day-old hamsters did not demo nstrate any inhibitory effect on the cell growth. Lysates from the rem nant liver 3 days after partial hepatectomy did not show any inhibitor y effect on the cell growth but lysates from the remnant liver 14 days after the operation came to show an appreciable inhibitory effect on the cell growth. An inhibitor of the cell growth was purified from adu lt hamster fiver by ammonium sulfate precipitation, DEAE-, hydroxyl ap atite-, phenyl Sepharose- and Sephadex G75 column chromatography. The cell growth inhibitor thus prepared was shown to be pure by an ion-exc hange chromatography, SDS-PAGE and analytical isoelectric focusing. Th e inhibitor was found to have a molecular mass of 37 kDa and an isoele ctric point of approx. 7.5 and to cause reversible arrest of the trans formed fibroblasts predominantly in the GO/G1 phase of the cell cycle at the concentration of approx. 0.9 mu g per ml.