Effects of potassium-magnesium citrate supplementation on cytosolic ATP citrate lyase and mitochondrial aconitase activity in leukocytes: a window on renal citrate metabolism.
BACKGROUND
An increase in urinary citrate excretion is associated with a decrease in activity of renal cortical cytosolic ATP citrate lyase (ACL) and mitochondrial aconitase (m-aconitase). Because potassium-magnesium citrate causes an increase in urinary citrate excretion, we decided to assess its effects on ACL and m-aconitase in the leukocytes of renal stone patients.


METHODS
Twenty male renal stone patients were supplemented with potassium-magnesium citrate twice daily (i.e. 42 mEq potassium, 21 mEq magnesium, and 63 mEq citrate per day) for a period of 1 month. Two 24-h urine and one 15-mL heparinized blood samples were collected from each patient before and after supplementation. Urine samples were analyzed for relevant biochemical compositions. Leukocytes were separated from blood samples by centrifugation and assayed for ACL and m-aconitase activity.


RESULTS
Supplementation with potassium-magnesium citrate significantly increased urinary pH (P < 0.005) and excretions of potassium (P < 0.001), magnesium (P < 0.001) and citrate (P < 0.0001). The activity of both ACL and m-aconitase were significantly decreased (P < 0.004 and P < 0.02 respectively). The decrease in ACL activity was inversely correlated with an increase in urinary excretion of both potassium (r = -0.620, P < 0.0001) and citrate (r = -0.451, P < 0.004). A similar inverse correlation was observed between m-aconitase activity and urinary excretion of citrate (r = -0.322, P < 0.043).


CONCLUSIONS
Changes in enzyme activity, related to citrate metabolism in leukocytes, might reflect the status of renal tubular cells.
Tosukhowong
Piyaratana
P
Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok.
Tungsanga
Kriang
K
Phongudom
Sumet
S
Sriboonlue
Pote
P
D001275:ATP Citrate (pro-S)-Lyase / Q000187:drug effects*; D000154:Aconitate Hydratase / Q000187:drug effects*; D000328:Adult; D019343:Citric Acid / Q000652:urine; D004232:Diuretics / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007669:Kidney Calculi / Q000201:enzymology; D007962:Leukocytes / Q000201:enzymology*; D008274:Magnesium / Q000652:urine; D017616:Magnesium Compounds / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000652:urine; D019357:Potassium Citrate / Q000494:pharmacology*; D014556:Urine / Q000737:chemistry
D004232:Diuretics; D017616:Magnesium Compounds; D019343:Citric Acid; D001275:ATP Citrate (pro-S)-Lyase; D000154:Aconitate Hydratase; D019357:Potassium Citrate; D008274:Magnesium; D011188:Potassium