Cytoskeleton disruption and apical redistribution of proximal tubule Na(+)-K(+)-ATPase during ischemia.
The polar distribution of Na(+)-K(+)-ATPase to the basolateral membrane of proximal tubule cells is essential for the efficient and vectorial reabsorption of Na+ and may be dependent on the formation of a metabolically stable, detergent-insoluble complex of Na(+)-K(+)-ATPase with the actin membrane cytoskeleton. The present studies utilized immunocytochemical techniques to demonstrate and quantify the apical redistribution of Na(+)-K(+)-ATPase during mild ischemia (15 min) that occurred in proximal (1.3 +/- 0.9 vs. 4.5 +/- 1.1 particles/100 microns surface membrane, P less than 0.01) but not distal tubule cells. Treatment of control apical membranes with 2-(2-methoxyethoxy)ethyl 8-(cis-2-n-octylcyclopropyl)octanoate (A2C), a fluidizing agent, markedly increased membrane fluidity without any effect on Na(+)-K(+)-ATPase activity. In brush-border membrane vesicles isolated after ischemia, however, A2C further increased an already elevated Na(+)-K(+)-ATPase activity. During ischemia, total cellular Na(+)-K(+)-ATPase activity remained unaltered, but the Triton X-100-soluble (noncytoskeleton associated) fraction of Na(+)-K(+)-ATPase increased significantly following 15 and 30 min. There was a corresponding decrease in the Triton X-100-insoluble fraction of Na(+)-K(+)-ATPase, with the ratio of detergent-soluble to -insoluble Na(+)-K(+)-ATPase increasing from 13 +/- 2 to 32 +/- 5% (P less than 0.01) during 30 min of ischemia. Western blot analysis of the Triton X-100-soluble fraction, following 30 min of ischemic injury, revealed the presence of Na(+)-K(+)-ATPase, actin, fodrin, and uvomorulin. However, in a fraction highly enriched for Na(+)-K(+)-ATPase, neither actin, fodrin, nor uvomorulin was detected.(ABSTRACT TRUNCATED AT 250 WORDS)
Molitoris
B A
BA
Department of Medicine, University of Colorado Health Science Center, Denver.
Dahl
R
R
Geerdes
A
A
D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology; D003599:Cytoskeleton / Q000201:enzymology / Q000648:ultrastructure*; D003902:Detergents; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D007511:Ischemia / Q000201:enzymology*; D007687:Kidney Tubules, Proximal / Q000201:enzymology*; D008297:Male; D017830:Octoxynol; D011092:Polyethylene Glycols; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D012995:Solubility; D014018:Tissue Distribution
D003902:Detergents; D011092:Polyethylene Glycols; D017830:Octoxynol; D000254:Sodium-Potassium-Exchanging ATPase