Impact of FeD and FeS on isolated tubule mitochondrial energetics, as assessed by ATP/ADP ratios. Impact of FeD and FeS on isolated tubule mitochondrial energetics, as assessed by ATP/ADP ratios. FeD did not alter ATP/ADP ratios, indicating a lack of mitochondrial damage. Conversely, FeS dramatically lowered ATP/ADP ratios, an effect that was not blocked by inhibiting NaK ATPase with ouabain (oua). Therefore, these results indicate that FeS but not FeD inhibits mitochondrial ATP production and, thus, likely explains why FeS but not FeD causes tubular cell death. Richard A. Zager CJASN 2006;1:S24-S31 ©2006 by American Society of Nephrology