Two K(+)-selective conductances in single proximal tubule cells isolated from frog kidney are regulated by ATP.
1. The whole-cell and single channel patch clamp techniques were used to identify K(+)-selective conductances in single proximal tubule cells isolated from frog kidney and to examine their ATP sensitivity. Whole-cell currents were inhibited by the K+ channel inhibitors Ba2+ and quinidine in a dose-dependent manner. Addition of Ba2+ alone, quinidine alone, or both inhibitors together revealed two separate conductances, one of which was blocked by both Ba2+ and quinidine (GBa)1, the other being sensitive to quinidine alone (Gquin). 2. With Na(+)-containing Ringer solution in the bath and K(+)-containing Ringer solution in the pipette, both currents were selective for K+ over Na+. The K+ : Na+ selectivity ratio of GBa was around 50:1, while that of Gquin was 4:1. In symmetrical KCl solutions GBa showed inward rectification, while Gquin demonstrated outward rectification. 3. In the absence of pipette ATP, both GBa and Gquin ran down over 10 min. However, when 2 mM ATP was included in the pipette GBa increased, while Gquin remained unchanged. 4. Single channel studies demonstrated that a basolateral K+ channel shared several of the characteristics of GBa. It was inhibited by both Ba2+ and quinidine, underwent run-down in excised patches in the absence of ATP, and was activated by ATP. 5. We conclude that cells of the frog proximal tubule contain at least two distinct K(+)-selective conductances, both of which are regulated by ATP, and which may be involved in pump-leak coupling.
Robson
L
L
Department of Physiology, University of Leeds, UK. l.robson@sheffield.ac.uk
Hunter
M
M
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D004347:Drug Interactions; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011802:Quinidine / Q000494:pharmacology; D011896:Rana temporaria
D015221:Potassium Channels; D001464:Barium; D000255:Adenosine Triphosphate; D011802:Quinidine