PubMed Health⌕ Search

Biomedical subjects

L Beaugé

Publications and source records attributed to L Beaugé.

76 records · Page 5Linked to original sources
PubMed1975

Non-pumped sodium fluxes in human red blood cells. Evidence for facilitated diffusion.

Unidirectional and net Na+ fluxes modified by changes in internal Na+ concentration ([Na+]i) were studied in human red blood cells incubated in K+-free solutions containing 10-minus 4 m ouabain. An increase in [Na+]i brought about (a) a reduction in net Na+ gain, (b) no change in Na+ influx, (c) a reduction in the rate constant for Na+ effux and (d) an increase in Na+ efflux. Similar reductions in net Na+ gain were observed when the changes in [Na+]i were carried out at constant [K+]i. In addition, the rate constant for 42K+ efflux was not affected by changes in [Na+]i. The electrical membrane potential (as determined from the chloride distribution ratio) was also constnat. Furosemide (10-minus 3 M) increased the net Na+ gain in concentration reduced Na+ efflux and increased Na+ influx: the magnitude of these effects was dependent onthe intracellular Na+. The reduction in the net Na+ gain as [Na+]i increased was unaffected by depletion of cellular ATP to values below 10 mumol/1 cells, and this effect was independent of the depletion method used

Adenosine Triphosphate↗
PubMed1975

The interaction of lithium ions with the sodium-potassium pump in frog skeletal muscle.

1. The effects of external Li on Na and K efflux as well as those on K influx were studied in high Na muscles from Rana pipiens. 2. In the absence of external Ba, substitution of K-free Li for K-free Mg resulted in an increase of both Na and K efflux. The additional of ouabain produced an inhibition of Na efflux and at the same time a marked increase in the efflux of K. 3. K permeability was greatly reduced by adding 2 mM-Ba to the incubation solutions. Under these conditions, Li gave rise to a ouabain sensitive Na efflux which was 57% of that in the absence of Ba. On the other hand, the efflux of K was only slightly increased and was not affected further by ouabain. 4. The activation curves of Na efflux against the stimulating cation concentration in Na-free Mg-Ba Ringer followed a more or less hyperbolic function for both K and Li. While half-maximal activation was attained at higher concentrations of Li than of K, the maximal efflux in Li was smaller than in K. 5. The extra Na efflux produced by K was increased when Li was added to the media. This increment was not a simple additive effect and was independent of the Li concentration. In addition, at some concentrations Li increased the ouabain-sensitive K influx, whereas at others it reduced it. 6. Reversible changes in membrane permeability to monovalent cations were accomplished by incubating the muscles in the presence of Nystatin, 50 mug/ml. When internal K was reduced to values around 1-2 mumole/g (using Li as a replacement), thus minimizing the possibility of K leaking out of the cells, both Ko and Lio were able to promote a ouabain-sensitive extra efflux of Na. 7. The residual Na efflux in (K+Na)-free solutions was not affected by the removal of Ca from the media in either Mg or Li solutions, both in the absence and the presence of Ba. On the other hand, the values for the residual efflux were higher in Mg (0-00228 min-1) than in Li (0.00135 min-1). 8. These results fully support the notion that Li ions have a K-like activating action on the Na pump in muscles. In addition, they suggest that some other kind of interaction may exist between Li and the Na-K pump.

Animals↗