EFFECT OF GLUCOSE ON PH(IN) AND [CA2-3T3 CELLS TRANSFECTED WITH THE YEAST P-TYPE H+-ATPASE(](IN) IN NIH)

NIH-3T3 cells transfected with yeast H+-ATPases (RN1a cells) are tumor igenic (Perona and Serrano, 1988, Nature, 334:438). We have previously shown that RN1a cells maintain a chronically high intracellular pH (p H(im)) under physiological conditions. We have also shown that RN1a ce lls are serum-independent for growth, maintain a higher intracellular Ca2+ ([Ca2+](in)), and glycolyze more rapidly than their non-transform ed counterparts (Gillies et al., Proc. Natl. Acad. Sci., 1990, 87:7414 ; Gillies et al., Cell. Physiol. Biochem., 1992, 2:159). The present s tudy was aimed to understand the interrelationships betwene glycolysis , pH(in), and [Ca2+](in) in RN1a cells and their non-transformed count erparts, NIH-3T3 cells. Our data show that the higher rate of glycolys is observed in RN1a cells is due to the presence of low affinity gluco se transporters. Consequently, the higher rate of glycolysis is exacer bated at high glucose concentration in RN1a cells. Moreover, the maxim al velocity (V-max) for glucose utilization is up to sixfold higher in RN1a cells than in the NIH-3T3 cells, suggesting that the number of g lucose transporters is higher in RN1a than NIH-3T3 cells. Glucose addi tion to NIH-3T3 cells results in modest decreases in both pH(in) and [ Ca2+](in). In contrast, RN1a cells respond to glucose with a large dec rease in pH(in), followed by a large decrease in [Ca2+](in). The decre ase in [Ca2+](in) observed upon glucose addition is likely due to acti vation of Ca2+-ATPase by glycolysis, since the Ca2+ decrease is abolis hed by the Ca2+ ATPase inhibitors thapsigargin and cyclopiazonic acid. Glucose addition to ATP-depleted cells results in a decrease in [Ca2](in), suggest ing that ATP furnished by glycolysis is utilized by thi s pump. (C) 1994 Wiley-Liss, Inc.