The role of P i in glycolytic inhibition of calcium ion uptake by ELD ascites tumor cells

Abstract

1. 1. In contrast to previous investigations at 25° C [1], glucose was shown to support 45Ca 2+ uptake at 37° C in intact ELD ascites tumor cells. 2. 2. Intact ascites tumor cells in vitro accumulated up to 5.0 μmol of 45Ca 2+ per g cells dry wt. within 20 min. 3. 3. In the presence of 10.0 mM glucose, intracellular P i levels fell from 40.0 μmol · g −1 cells dry wt. to 20.0 μmol · g −1 cells dry wt. in 5 min. 4. 4. Intracellular P i levels were maintained by 20.0 mM extracellular Tris-P i. 5. 5. 45Ca 2+ uptake was inhibited in P i-depleted cells, even though the metabolic rate (as measured by Q lactate ) and energy state (as measured by ATP levels) were at acceptable levels [2]. 6. 6. Evidence has been presented suggesting that previous reports of glucose inhibition of calcium uptake can be attributed to a competition for available intracellular P i between glycolytic processes and the mitochondrial calcium uptake mechanism.