ACTIVE POTASSIUM TRANSPORT AND [Na⁺+ K⁺]ATPase ACTIVITY IN CULTURED GLIOMA AND NEUROBLASTOMA CELLS

Abstract

—The ouabain‐sensitive K+ uptake and ATPase activities of cultured glioma and neuroblastoma cells were studied. Both cell lines showed ouabain‐sensitive K+ uptake which correlated with the level of [Na++ K+]ATPase activity found in the respective total cell homogenate. The glioma cells had a 2.1‐fold higher rate of K+ uptake than neuroblastoma cells, and a 2.4‐fold higher [Na++ K+]ATPase activity. In the presence of ouabain neuroblastoma cells released K+ and took up Na+ in a 1:1 ratio. These results are compared and contrasted with similar studies on brain tissue and isolated cells. It is suggested that the cultured cell lines may serve as good models for the cation transport properties of their tissue counterparts.

Alterations of hepatic Na + ,K + -ATPase and bile flow by estrogen: Effects on liver surface membrane lipid structure and function

“…Previous studies (7, 36, 39) also suggest an important role for membrane viscosity in controlling the activity of Na+,K+-ATPase in that there is a good correlation between membrane lipid phase transitions and Arrhenius activation energies. Indeed, Kimelberg and Papahadjopoulis have speculated that membrane cholesterol accumulation may impair Na+,K+-ATPase activity through changes in membrane structure (7). The results of the present study support these previous studies and suggest that the synthetic estrogen, ethinyl estradiol, decreases hepatic Na+,K+-ATPase activity through changes in surface membrane lipid structure.…”

“…Studies of membrane structure and function both in vivo and in vitro suggest that alterations in lipid composition may alter Na+,K+-ATPase function and bile flow. Na+,K+-ATPase (ATP phosphohydrolase, EC 3.6.1.3) is a mammalian surface membrane that is sensitive to the lipid structure of the membrane bilayer (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)). An important function of Na+,K+-ATPase in the hepatocyte may be the active secretion of sodium into the bile canaliculus, thus driving water across the canalicular membrane (8,9).…”

Activation of Muscarinic Cholinergic Receptors on Human SH-SY5Y Neuroblastoma Cells Enhances Both the Influx and Efflux of K+under Conditions of Hypo-Osmolarity

“…The ability of Oxo-M to regulate the concentration of K ϩ in SH-SY5Y cells under conditions of isotonicity (340 mOsM), mild hypotonicity (290 mOsM), or moderate hypotonicity (230 mOsM) was evaluated in the absence or presence of inhibition of K ϩ influx after a 10-min incubation. Under isotonic conditions, the intracellular K ϩ concentration, as determined by means of a K ϩ -specific electrode, was 1.22 mol K ϩ /mg protein, a value consistent with previous measurements of intracellular K ϩ in the neuroblastoma 2A cell line (ϳ1 Eq K ϩ /mg protein; Kimelberg, 1974). Because the intracellular water space for SH-SY5Y cells was determined to be 8.5 l/mg protein (n ϭ 3), the intracellular K ϩ concentration of SH-SY5Y cells was calculated to be approximately 140 mM.…”

Abnormal sodium pump distribution during renal tubulogenesis in congenital murine polycystic kidney disease.

“…The mechanism(s) of inactivation of Na+/K+-ATPase at the apical membrane is unknown. However, previous studies indicate that Na+/K+-ATPase activity is downregulated by decreased fluidity ofthe lipid bilayer (43). In normal polarized epithelial cells, the apical membrane contains a high concentration of glycosphingolipids compared with the basal-lateral membrane (44).…”