title: Evidence for role of cytosolic free calcium in hypoxia-induced proximal tubule injury.
abstract: The role of cytosolic free Ca2+ ([Ca2+]i) in hypoxic injury was investigated in rat proximal tubules. [Ca2+]i was measured using fura-2 and cell injury was estimated with propidium iodide (PI) in individual tubules using video imaging fluorescence microscopy. [Ca2+]i increased from approximately 170 to approximately 390 nM during 5 min of hypoxia. This increase preceded detectable cell injury as assessed by PI and was reversible with reoxygenation. 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA; 100 microM) reduced [Ca2+]i under basal conditions (approximately 80 nM) and during hypoxia (approximately 120 nM) and significantly attenuated hypoxic injury. When [Ca2+]i and hypoxic cell injury were studied concurrently in the same individual tubules, the 10 min [Ca2+]i rise correlated significantly with subsequent cell damage observed at 20 min. 2 mM glycine did not block the rise in [Ca2+]i, yet protected the tubules from hypoxic injury. These results indicate that in rat proximal tubules, hypoxia induces an increase of [Ca2+]i which occurs before cell damage. The protective effect of BAPTA supports a role for [Ca2+]i in the initiation of hypoxic proximal tubule injury. The glycine results, however, implicate calcium-independent mechanisms of injury and/or blockade of calcium-mediated processes of injury such as activation of phospholipases or proteases.
authors.affiliation: Department of Medicine, University of Colorado School of Medicine, Denver 80262.
authors.forename: A
authors.initials: A
authors.lastname: Kribben
authors.forename: E D
authors.initials: ED
authors.lastname: Wieder
authors.forename: J F
authors.initials: JF
authors.lastname: Wetzels
authors.forename: L
authors.initials: L
authors.lastname: Yu
authors.forename: P E
authors.initials: PE
authors.lastname: Gengaro
authors.forename: T J
authors.initials: TJ
authors.lastname: Burke
authors.forename: R W
authors.initials: RW
authors.lastname: Schrier
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015687:Cell Hypoxia; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008856:Microscopy, Fluorescence; D011188:Potassium / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D014700:Verapamil / Q000494:pharmacology; D014741:Video Recording
chemical_list: D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D014700:Verapamil; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D011188:Potassium; D002118:Calcium; D005998:Glycine