INFLUENCE OF CLONED VOLTAGE-GATED K-VOLUME( CHANNEL EXPRESSION ON ALANINE TRANSPORT, RB+ UPTAKE, AND CELL)

Voltage-gated K+ channels are involved in regulation of action potenti al duration and in setting the resting membrane potential in nerve and muscle. To determine the effects of voltage-gated K+ channel expressi on on processes not associated with electrically excitable cells, we s tudied cell volume, membrane potential, Na+-K+-ATPase activity, and al anine transport after the stable expression of the Kv1.4 and Kv1.5 hum an K+ channels in Ltk- mouse fibroblasts (L-cells). The fast-activatin g noninactivating Kv1.5 channel, but not the rapidly inactivating Kvl. 4 channel, prevented dexamethasone-induced increases in intracellular volume and inhibited Na+-K+-ATPase activity by 25%, as measured by Rb- 86+ uptake. Alanine transport, measured separately by systems A and AS C, was lower in Kvl.5-expressing cells, indicating that the expression of this channel modified the Na+-dependent amino acid transport of bo th systems. Expression of the Kvl.4 channel did not alter alanine tran sport relative to wild-type or sham-transfected cells. The changes spe cific to Kvl.5 expression may be related to the resting membrane poten tial induced by this channel (-30 mV) in contrast to that measured in wild-type sham-transfected, or Kvl.4-transfected cells (-2 to 0 mV). B locking of the Kvl.5 channel by 60 muM quinidine negated the effects o f Kvl.5 expression on intracellular volume, Na+-K+-ATPase, and Na+-dep endent alanine transport. These results indicate that delayed rectifie r channels such as Kvl.5 can play a key role in the control of cell me mbrane potential, cell volume, Na+-K+-ATPase activity, and electrogeni c alanine transport across the plasma membrane of electrically unexcit able cells.