ZIB

Hits per page

hits 1 - 2 | 2 hits

Sorting

Electronic Resource

Mechanism and role of furosemide-sensitive K+ transport in L cells: A genetic approach (1980)

Gargus, J. J. ; Slayman, C. W.

Springer

The journal of membrane biology 52 (1980), S. 245-256

add to mindlist on the mindlist

Details

ISSN: 1432-1424

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary As part of a genetic study of the mechanisms for cation transport in cultured mammalian cells, two mouse fibroblastic cell lines have been compared with respect to unidirectional42K+ influx. The cell lines areLM(TK −) andLTK-5, a mutant selected fromLM(TK −) by the ability to grow in medium containing 0.2mm K+. In both cell lines, the overall influx can be resolved into three components: (i) a ouabain- and vanadate-sensitive component ( i MK f), presumably the Na/K pump, which is a saturable function of extracellular K+ with aK 1/2 of 1.3mm; (ii) a furosemide-sensitive component ( i Mk fx), also a saturable function of extracellular K+, with aK 1/2 of 6mm; and (iii) a diffusional component ( i Mk d); which is a linear function of extracellular K+. By several independent criteria, i Mk o and i Mk f appear to be distinct transport processes. First, as indicated above, they can be separated with the use of inhibitors. In addition, they can be separated genetically, since theLTK-5 mutant shows a threefold elevation in i Mk f with no change in i Mk o. And finally, extracellular Na+ has no effect on i Mk o, but stimulates i Mk f, a result consistent with the notion that i Mk f influx occurs by Na−K cotransport. Further experiments were directed towards understanding the nature of theLTK-5 mutation and the physiological role of i Mk f. LTK-5 differs from the parental cell line, not only in having an increased i Mk f, but also in having a large cell volume, a slow maximal growth rate, and an ability to grow at 0.2mm K+. The most straightforward interpretation — that the increased i Mk f is itself responsible—is unlikely since the addition of furosemide to the growth medium had no effect upon the growth rate or cell volume of the mutant at either normal or low extracellular K+ concentrations. It did, however, render the parent capable of growth at 0.2mm K+. Possible interpretations are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01869193

Permalink

Library	Location	Call Number	Volume/Issue/Year	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

Electronic Resource

Rapid changes in bidirectional K+ fluxes preceding DMSO-induced granulocytic differentiation of HL-60 human leukemic cells (1984)

Gargus, J. J. ; Adelberg, E. A. ; Slayman, C. W.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 120 (1984), S. 83-90

add to mindlist on the mindlist

Details

ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: When grown in medium containing 5 mM potassium and 140 mM sodium, HL-60, a human promyelocytic cell line, maintained a steady-state intracellular K+ concentration of 145 mmol/L cells and a steady-state intracellular Na+ concentration of 30 mmol/L cells. Nearly 90% of the unidirectional 42K+ influx could be inhibited by the cardiac glycoside ouabain with a Ki of 5 × 10-8 M. This ouabain-sensitive component of influx rose as a saturating function of the extracellular K+ concentration with a K1/2 of 0.85 mM. The component of 42K+ influx resistant to ouabain inhibition was a linear function of the extracellular K+ concentration and was insensitive to inhibition by the diuretic furosemide. Unidirectional K+ efflux followed first order kinetics with a half-time of 55 min. Addition of 1.5% dimethyl sulfoxide (DMSO) to a culture of HL-60 cells allowed two population doublings followed by the cessation of growth without an impairment of cell viability. Beginning 2 to 3 days after DMSO addition, the cells underwent a dramatic reduction in volume (from 925 μm3 to 500 μm3) and began to take on the morphological features of mature granulocytes. Throughout this process of differentiation there was no change in the intracellular sodium or potassium concentration. However, immediately following the addition of DMSO to a culture of cells, there began an immediate, coordinated reduction in bidirectional K+ flux. The initial rate of the ouabain-sensitive component of K+ influx fell with a half-time of 11 h to a final rate, at 6 days induction, equal to one ninth that of the uninduced control, and over the same period, the rate constant for K+ efflux fell with a half-time of 14 h to a final value one fourth that of the uninduced control. The rapidity with which these flux changes occur raises the possibility that they play some role in the control of subsequent events in the process of differentiation.

Additional Material: 8 Ill.