Lack of changes in cytosolic ionized calcium in primary cultures of rat kidney cortical cells exposed to cytotoxic concentrations of gentamicin.
Gentamicin nephrotoxicity in vivo has a delayed onset. Our assessment of gentamicin-induced cell death in vitro, by measuring the release of cytosolic lactate dehydrogenase (LDH), indicated a prolonged onset as well. A recent study, which showed that gentamicin caused an abrupt increase in the concentration of cytosolic free calcium ([Ca2+]i) in a trypsin-harvested kidney cell line, suggested that immediate changes in calcium homeostasis may initiate the pathogenesis of gentamicin nephrotoxicity. To study the immediate effect of gentamicin on [Ca2+]i, gentamicin was perfused for 1 hr over primary monolayer cultures of renal cortical epithelial cells, and suspensions of trypsin-harvested renal cells (from primary cultures and a cell line) were treated with gentamicin for 30 min. [Ca2+]i was determined using the fluorescent probe fura-2. Positive controls (ionomycin and mercury) reliably increased [Ca2+]i in each experimental model, but no increase in [Ca2+]i was observed with gentamicin. Because enzyme release data indicated that significant cytotoxicity did not occur until 48 hr of exposure to 2 mM gentamicin, primary cultures were exposed to gentamicin (1-2 mM) for 24-48 hr and [Ca2+]i was measured. No gentamicin-induced increase in [Ca2+]i was observed in these longer exposures, whether or not significant LDH release occurred. These results do not support a role for elevated [Ca2+]i in the cytotoxicity of gentamicin in cultured kidney cells, either immediately after exposure or following prolonged exposures.
Swann
J D
JD
Division of Pharmacology/Toxicology, College of Pharmacy, University of Texas, Austin 78712.
Ulrich
R
R
Acosta
D
D
D000818:Animals; D002118:Calcium / Q000032:analysis*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005839:Gentamicins / Q000633:toxicity*; D015759:Ionomycin / Q000494:pharmacology; D007672:Kidney Cortex / Q000187:drug effects* / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014357:Trypsin / Q000494:pharmacology
D005839:Gentamicins; D015759:Ionomycin; D007770:L-Lactate Dehydrogenase; D014357:Trypsin; D002118:Calcium