Mitochondrial injury: an early event in cisplatin toxicity to renal proximal tubules.
Oxygen consumption (QO2) and net K+ transport were studied in rabbit proximal tubule suspensions to define the early effects of cisplatin on proximal tubule function. Cisplatin caused dose-dependent inhibition of QO2, which was delayed in onset. The concentration of cisplatin required for inhibition decreased as the duration of exposure was increased [40-min exposure, threshold concentration of 10(-4) M, inhibitor constant (Ki) of 10(-3) M; 4-h exposure, threshold concentration of 3 X 10(-5) M, Ki of 10(-4) M]. Both ouabain-sensitive and ouabain-insensitive QO2 were reduced, indicating inhibition of all adenosinetriphosphatases, including Na(+)- K(+)-ATPase activity. There was a parallel fall in ouabain-sensitive net K+ transport and cytosolic K+ content, confirming the latter observation. Na(+)-K(+)-ATPase activity was unchanged in cell membranes prepared by hypotonic lysis from cisplatin-treated tubules, indicating an indirect cytosol-dependent mechanism of enzyme inhibition. Nystatin-stimulated QO2 was reduced in cisplatin-treated tubules, excluding inhibition of Na+ entry as the mechanism of injury and suggesting mitochondrial injury. The latter was confirmed by measurement of carbonylcyanide-m-chlorophenylhydrazone (CCCP)-uncoupled QO2 in intact cells and ADP-stimulated (state 3) QO2 in digitonin-permeabilized tubules. Furthermore, by maximally stimulating mitochondrial respiration with CCCP and nystatin, it was possible to demonstrate mitochondrial injury at a time when basal QO2 and K+ transport were apparently normal. These data suggest that mitochondrial injury is a central event in cisplatin toxicity to the proximal tubule.
Brady
H R
HR
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Kone
B C
BC
Stromski
M E
ME
Zeidel
M L
ML
Giebisch
G
G
Gullans
S R
SR
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002945:Cisplatin / Q000506:poisoning*; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects*; D009761:Nystatin / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D009761:Nystatin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D010042:Ouabain; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D002945:Cisplatin; D011188:Potassium