Measurement of Na-K pump current in acinar cells of rat lacrimal glands.
Isolated cells from rat lacrimal glands were voltage clamped using the tight-seal whole-cell recording technique. The intracellular solution contained ATP and an elevated Na concentration (70 mM). Removing external K ions elicited an inward current shift. Ouabain (0.5 mM) induced an inward current shift of identical amplitude, but with slower kinetics. In the presence of ouabain, removal of K ions did not alter the cell current. The potassium- and ouabain-sensitive current was outward between -120 and +20 mV, and its amplitude decreased below -60 mV. This current was highly sensitive to temperature, and was not affected by blockers of the K channels which are present in these cells. It was attributed to an inhibition of the Na-K pump. The Na-K pump current was estimated to be 15 pA for an average acinar cell at physiological temperature, with 70 mM internal Na ions and 20 mM external K ions. Implications of this value in terms of electrolyte secretion are discussed.
Dipolo
R
R
IVIC-Department of Biophysics, Caracas, Venezuela.
Marty
A
A
D000818:Animals; D002478:Cells, Cultured; D004553:Electric Conductivity; D007700:Kinetics; D007765:Lacrimal Apparatus / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase