Mechanism of apical K+ channel modulation in principal renal tubule cells. Effect of inhibition of basolateral Na(+)-K(+)-ATPase.
The effects of inhibition of the basolateral Na(+)-K(+)-ATPase (pump) on the apical low-conductance K+ channel of principal cells in rat cortical collecting duct (CCD) were studied with patch-clamp techniques. Inhibition of pump activity by removal of K+ from the bath solution or addition of strophanthidin reversibly reduced K+ channel activity in cell-attached patches to 36% of the control value. The effect of pump inhibition on K+ channel activity was dependent on the presence of extracellular Ca2+, since removal of Ca2+ in the bath solution abolished the inhibitory effect of 0 mM K+ bath. The intracellular [Ca2+] (measured with fura-2) was significantly increased, from 125 nM (control) to 335 nM (0 mM K+ bath) or 408 nM (0.2 mM strophanthidin), during inhibition of pump activity. In contrast, cell pH decreased only moderately, from 7.45 to 7.35. Raising intracellular Ca2+ by addition of 2 microM ionomycin mimicked the effect of pump inhibition on K+ channel activity. 0.1 mM amiloride also significantly reduced the inhibitory effect of the K+ removal. Because the apical low-conductance K channel in inside-out patches is not sensitive to Ca2+ (Wang, W., A. Schwab, and G. Giebisch, 1990. American Journal of Physiology. 259:F494-F502), it is suggested that the inhibitory effect of Ca2+ is mediated by a Ca(2+)-dependent signal transduction pathway. This view was supported in experiments in which application of 200 nM staurosporine, a potent inhibitor of Ca(2+)-dependent protein kinase C (PKC), markedly diminished the effect of the pump inhibition on channel activity. We conclude that a Ca(2+)-dependent protein kinase such as PKC plays a key role in the downregulation of apical low-conductance K+ channel activity during inhibition of the basolateral Na(+)-K(+)-ATPase.
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
W H
WH
Wang
J
J
Geibel
G
G
Giebisch
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D006863:Hydrogen-Ion Concentration; D015759:Ionomycin / Q000494:pharmacology; D007684:Kidney Tubules / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019311:Staurosporine; D013327:Strophanthidin / Q000494:pharmacology
D000470:Alkaloids; D015221:Potassium Channels; D015759:Ionomycin; D013327:Strophanthidin; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D019311:Staurosporine; D002118:Calcium