Effect of Rb+ Substituted for K+ on HeLa Cells: Cellular Content and Membrane Transport of Monovalent Cations, and Cell Growth

Abstract

ABSTRACT. The usefulness of Rb+ was investigated as an analog of K+ in membrane transport and in supporting the growth of HeLa cells. On replacement of extracellular K+ by Rb+, intracellular Rb+ content increased linearly at 15 min. K+ content declined in contrast with Rb+, but Na+ content was unaffected. In Rb+-preloaded cells, Rb+ and K+ were exchanged after replacement of extracellular Rb+ with K. A kinetic analysis of intracellular Rb+ content showed that most K+ was exchangeable with Rb+, but a small part of K+ was not. Both Rb+ and K+ influxes were equally inhibited by ouabain or furosemide. Rb+ efflux was repressed by furosemide, whereas K+ efflux was not influenced. When 90 % of K+ was replaced by Rb+ in serum-free chemically defined medium, cell growth and protein synthesis were inhibited. After total replacement of extracellular K+ by Rb+, cell growth ceased and cellular protein content decreased, while a small part of intracellular K+ remained unexchanged. HeLa cells seemed to accumulate Rb+ in preference to K+.

Interrelation between membrane transport and the contents of alkali metal cations in HeLa cells.

“…Nevertheless, Rb+ was shown to behave similarly to K+ in membrane transport when influx measurements were carried out in short-term experiments lasting a few hour (MIYAMOTO et al, 1978b). Therefore, Rb+ has been used as an analog for K+ to investigate cation transport, and cell K+ plus Rb+ can be taken as cell K+ in HeLa cells as observed in the normal medium.…”

“…5). The inhibitors included carbonyl cyanide m-chlorophenylhydrazone and 2-deoxyglucose, which affected the cation pumping by reducing the cellular ATP contents (unpublished data) ; and ouabain and furosemide, which abolished the cation pumping and the ouabain-insensitive Rb+ : K+ exchange diffusion, respectively (TUPPER, 1975;MIYAMOTO et al, 1978b). Since cell cations were not yet in complete equilibrium after 2-hr treatment with ouabain, the preserved contents of K+ plus Rb+ (40 % in average) would still decrease with time.…”

Kinetics of hyperosmotically stimulated Na-K-2Cl cotransporter in Xenopus laevis oocytes

“…In brief, groups of 20 -25 oocytes were incubated for 24 h with L15 containing 1 Ci/ml of either 22 Na, 86 Rb, or 36 Cl. Preliminary experiments have shown that oocytes injected with NKCC1 cRNA and constitutively active SPAK cRNA equilibrate the isotopes to the outside specific activity within 12-24 h. After two 5-l samples were collected to calculate the outside specific activity, the oocytes were rapidly washed four times with ice-cold L15 and individually counted.…”

Stimulating Effect of an Artificial Electron Mediator, Phenazine Methosulfate, on Rb<SUP>+</SUP> Transport in HeLa Cells

“…Simultaneous treatments of cells with PMS and ouabain reduced the ATP contents significantly, whereas treatment with PMS or ouabain alone did not change the level significantly in comparison to the control in the presence of CCCP. The intracellular contents of Rb+ plus K+, which are identical with K+ contents of cells incubated in normal medium (18), increased slightly in the presence of PMS (Fig. 7); but, Nat was not significantly changed by the same treatment.…”

“…But, the effects of PMS on cellular functions seems to be closely related to the chemical characteristics of PMS, regardless of the cell species. We previously reported that when the K+ in the medium was replaced totally with Rb+, Rb+ substituted for K+ in the membrane transport of HeLa cells (18). Using techniques described in that same report, we recently have found that PMS stimulates active Rb+ uptake in the same cells.…”