Effect of ouabain and metabolic inhibitors on the Na and K movements of nucleotide contents of L cells

摘要

1. The general characteristics and Na and K movements of L cells (derived from mouse epithelium) have been measured. Both cells grown in suspension (LS cells) and as a monolayer (L cells) were used.2. The volume of L cells was 1·2 × 10^-9 cm³ and of LS cells 3·5 × 10^-9 cm³; of this 82% was water.3. Electron micrographs showed the presence of numerous protrusions (filopodia) from both forms of the cell. These had the effect of increasing the surface area of the cell by 2-4 times over smooth cells of the same volume. On changing from the flattened to the spherical shape during trypsinization, the filopodia altered to maintain a constant V/A ratio.4. These cells contain K, about 170 m-mole/l. intracellular water and Na, 9 m-mole/l. intracellular water (L cells only) at 20° C. The K fluxes are 1·9 p-mole/cm² sec for LS cells and 0·8 p-mole/cm² sec for L cells and the Na fluxes are 1·8 p-mole/cm² sec for L cells (expressed as per total cell surface (including filopodia)). If expressed as p-mole/cell per sec then L and LS cells have the same K flux.5. 10^-4 M ouabain reduces the K influx to half, indicating an insensitivity to the glycosides common to the species. In the prolonged presence of ouabain the cells come into a new steady state with a [K]1, of 140 and a [Na]1 of 20-30 m-mole/l. intracellular water, but a constant [Na + K]1.6. Both DNP (10^-3 M) and IAA (10^-4 M) are required for maximum inhibition of K uptake, as both aerobic and anaerobic metabolic pathways may be used to drive the pump.7. K removal decreases the Na efflux, and Na removal (eventually) decreases the K influx providing evidence for Na/K coupling.8. The cells contain 7·5 m-mole/litre intracellular water of ATP, a level some 15 times that of ADP.9. The Na pump in these cells is very similar to that found in other tissues in that (a) it requires K to work, (b) it is blocked by ouabain and metabolic inhibitors and (c) it transports three molecules of Na for each two molecules of K.