1. Renal citrate metabolism and urinary citrate excretion in the infant rat.
- Author
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Melnick, Joel Z., Preisig, Patricia A., Alpern, Robert J., Baum, Michel, Melnick, J Z, Preisig, P A, Alpern, R J, and Baum, M
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CITRATES , *KIDNEY stones , *METABOLISM , *AGING , *ANIMAL experimentation , *ANIMAL populations , *CARRIER proteins , *COMPARATIVE studies , *DIET , *KIDNEYS , *RESEARCH methodology , *MEDICAL cooperation , *POTASSIUM , *RATS , *RESEARCH , *RESEARCH funding , *EVALUATION research - Abstract
Background: Although hypercalciuria has the same prevalence in children as adults, children rarely develop renal stones. This may be explained by a greater urinary citrate excretion in infants compared with adults. The present study examines the renal excretion of citrate and renal cortical citrate metabolism in infant and adult rats.Methods: Adult male and newly weaned infant rats were acclimated to metabolic cages and fed synthetic diets. Urine was collected after two days, and renal cortical citrate metabolism was assayed.Results: Infant rats had a lower plasma [HCO3-] and higher plasma [K+] and had a fourfold higher urinary citrate:creatinine ratio and a twofold higher concentration of citrate in their urine compared with adult rats. This higher urinary citrate excretion was not due to a difference in renal proximal tubular Na/citrate cotransporter activity, nor renal cortical citrate synthase or ATP citrate lyase activities in infants as compared with adults. However, infant rat kidneys had significantly lower mitochondrial aconitase (m-aconitase) activity. Renal cortical citrate concentrations were comparable in infant and adult rats. Manipulation of plasma [K+] to adult levels did not affect the higher urinary citrate excretion in infant rats.Conclusions: Urinary citrate excretion in infant rats is greater than in adults but does not parallel tissue [citrate]. Thus, this higher urinary citrate is likely due to maturational differences in the proximal tubule, other than Na/citrate cotransport, that directly affect citrate transport. [ABSTRACT FROM AUTHOR]- Published
- 2000
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