Changes in Microsomal Na⁺, K⁺-, Mg²⁺- and Ca²⁺-ATPase Activities during Proliferation of Chinese Hamster V-79 and Human HeLaS-3 Cells

Abstract

Changes in microsomal Na⁺, K⁺-, Mg²⁺- and Ca²⁺-ATPase activities during cell proliferation were examined in Chinese hamster V-79 (V-79) cells (normal cells) and human HeLaS-3 (HeLaS-3) cells (malignant cells). For V-79 cells, the Mg²⁺-ATPase activity per cell (pmol Pi/h/cell) in the confluent phase was higher than that in the logarithmically growing (log) phase. The amount of microsomal protein per cell was also high in the confluent phase. Specific activities (μmol Pi/h/mg protein) of Na⁺, K⁺-, Mg²⁺- and Ca²⁺-ATPases were significantly lower in the confluent phase than in the log phase. For HeLaS-3 cells, an increase in Ca²⁺-ATPase activity per cell was observed. The amount of microsomal protein per cell did not change between the log and confluent phase. The specific activity of Ca²⁺-ATPase in the confluent phase was also markedly higher than in the log phase. The relation between changes in ATPase activities and cell proliferation is discussed.