Pasteur Effect in Novikoff Ascites-hepatoma Cells.

Inhibition of fermentation or of glucose uptake in the presence ofoxygen has been observed in many forms of life and is generally referred to as the 'Pasteur effect'. In most tissues, oxidative inhibition of fermentation (ethanol or lactate production) is reflected by a parallel decrease in glucose consumption. Since certain tissues utilize lactate significantly, estimation of the Pasteur effect on the basis ofglucose uptake is a preferred determination. Many theories have been put forward for explaining the Pasteur effect and the two foremost ones are mentioned here. One assumes a localized deficiency ofADP or Pi in the soluble part ofthe cell cytoplasm resulting in low glycolytic ATP availability for glucose phosphorylation (Wu & Racker, 1959b). The other suggests an inhibition of phosphofructokinase and hexokinase by the high concentrations of ATP and glucose 6-phosphate observed aerobically (Passonneau & Lowry, 1962; Wu, 1964). Thus the former theory implies that aerobically produced ATP cannot be utilized for glucose phosphorylation, and the latter suggests that in aerobic conditions the high concentration of ATP is in the soluble part, inhibits phosphohexokinase and raises the concentration of glucose 6-phosphate such that hexokinase inhibition is elicited. Whether the two opposing theories can be tested becomes of importance in the understanding of the Pasteur effect. Novikoff ascites-hepatoma cells have been shown to have a high rate of glycogen formation from glucose (Nigam, 1964) and might serve as a test system. The present paper describes the type of Pasteur effect obtained in Novikoff ascites-hepatoma cells. Novikoff ascites-tumour cells were obtained as described by Nigam (1962). A known volume of washed tumour cells was suspended in the tris incubation medium of Wu & Racker (1959a). A 0-9ml. portion of the suspension (0.16ml. of packed cells) was transferred to ten 20ml. beakers and dinitrophenol was added to half of these to give 0*25mi concentration. After a preincubation of 5min. at 370 in a Dubnoff metabolic shaker flushed with oxygen, 10p,moles of [14C]glucose (105counts/min.) was added to each beaker (final volume, 1 ml.) and samples were withdrawn at