Single proximal tubules of Necturus kidney. VI: Nature of potassium transport

¹ Biophysical Laboratory, Harvard Medical School, Boston, Massachusetts

K concentration and apparent unidirectional K fluxes have been measured in Necturus kidney proximal tubule. Mean tubular K in 12 collections from the most distal segment of the tubule is 5.4 ± 0.3 mm, and the tubular K to serum K ratio in these experiments is 1.6 ± 0.1, not significantly different from the inulin concentration ratio, 1.4 ± 0.2. The glomerular fluid to serum K concentration ratio is 1.01 ± 0.03. Apparent unidirectional K fluxes were measured using stopped-flow microperfusion technique in 11 experiments with perfusion fluid containing about 7 mm K. The apparent mean K influx was 52 ± 6 pmoles/cm² sec and the apparent efflux was 49 ± 3 pmoles/ cm² sec.