Histochemical studies of adenosine triphosphatase activity of liver cells exposed to ribonuclease

It has been revealed that ribonuclease (RNase) can penetrate into living cells and inhibits amino acid incorporation into proteins resulting in the suppression of protein synthesis and growth of living cells. BHIDE, BRACHET¹, KAUFMAN and DAs have proven that the RNase penetrates into onion root-tip cells and induces a number of mitotic abnormalities. KIMOTO and others² also have revealed that RNase injection into mice results in the reduction of cytoplasmic basophilia with the morphologic change of endoplasmic reticulum and the disturbances in DNA synthesis as demonstrated histochemically on pancreatic exocrine cells and liver cells. But there is little information so far on the mechanisms of penetration of RNase into living cells. PILLERI³ and SCHUMAKER4 in Brachet's laboratory have demonstrated the uptake of RNase by pinocytosis in amoebae and cancer cells. This may suggest the penetration of RNase through the membrane of the endoplasmic reticulum in the cells whose RNase contents are low5, however it is reasonablly supposed that some phosphatase may be concerned with the permeability of RNase.