Rb⁺ influx in response to changes in energy generation: Effect of the regulation of the ATP content of HELa cells

Abstract

The effect of changes in energy metabolism on Rb+ influx was studied in HeLa cells. Irrespective of whether ATP production was controlled by varying the activity of glycolysis or of oxidative metabolism on addition of certain combinations of glucose, carbonylcyanide m-chlorophenylhydrazone, monoiodoacetic acid, and quercetin, Rb+ influx changed as a linear function of the ATP content, which varied in a wide range up to the normal level (15-20 nmol/mg protein or 3-4 mM). The difference between results obtained by these procedures was not significant. As the intracellular Na+ content varied at different ATP contents, the Na+ content was adjusted to similar levels by chilling the cells with varying ATP contents. However, a linear relation was still observed. A similar dependence was also obtained for cytoplasmic ATP, which would be more closely connected with the Na,K-pump than total ATP. The ratio of ouabain-sensitive Rb+ influx to the corresponding part of lactate production was nearly 2 in the presence of 2 mM glucose. From these results it is concluded that (1) active Rb+ influx, which is chiefly maintained by energy generated through glycolysis, can also be supported by oxidative metabolism; (2) Rb+ influx is regulated linearly as a function of the cellular ATP content up to the control level; but does not increase if ATP is raised still further; and (3) 2 Rb+ ions move concomitantly at the expense of one ATP molecule.

α-Adducin mutations increase Na/K pump activity in renal cells by affecting constitutive endocytosis: implications for tubular Na reabsorption

“…It may be speculated that ATP concentration in MDCK cells, but not in HEK, is limiting for Na-K-ATPase activity, in keeping with the previously demonstrated effect of adducin that increases Na-K-ATPase activity by enhancing the affinity for ATP (11). This may be supported by studies in HeLa and intact renal tubular cells, where pump activity changes as linear function of the ATP content (20,40). As opposed to MDCK cells, HEK exhibit high K influx per site, but it is well known that HEK are very different from MDCK, as they are not polarized and do not form tight junctions (44).…”

ATP and the Regulation of Renal Cell Function

“…The differences between the results obtained using broken membrane fragments and intact tubules may have been due to differ ences between the constituents of the ATPase hydrolytic assay medium and the intracellular milieu of the proximal tubule, including ADP, Pi> magnesium, and other cellular factors known to alter Na,K-ATPase activity. In a different study, a linear dependence of rubidium (potassium) transport on the A TP content was observed using HeLa cells, a nonepithelial preparation, and there was no difference in the linear relationship whether the A TP was produced by aerobic glycolysis or oxidative phosphorylation (47). These results, along with those in the kidney, suggest that at least under some conditions transport activity may be directly dependent on the concentration of ATP.…”

Relationships between the neuronal sodium/potassium pump and energy metabolism. Effects of K+, Na+, and adenosine triphosphate in isolated brain synaptosomes.

“…However, several studies have shown that in isolated cells from various sources, the rates of ouabain-sensitive K + (or S6Rb) transport increase linearly with a rise in [ATP] to 8-10 mM (Ikehara et al, 1984;Soltoff and Mandel, 1984;Tessitore et al, 1986). If this were true for the CNS cells as well, one could surmise that the neuronal Na pump in vivo may not operate at its maximal capacity.…”