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Hepatic and renal contributions to valproic acid-induced hyperammonemia
A M Marini1, B S Zaret, R R Beckner
1National Institute of Health, Bethesda, MD 20205.
Neurology
|March 1, 1988
Summary
Valproic acid (VPA) causes hyperammonemia in rats by inhibiting liver function, not kidney function. This effect is dose-dependent and linked to reduced carbamyl phosphate synthetase I activity.
Area of Science:
- Biochemistry
- Toxicology
- Pharmacology
Background:
- Valproic acid (VPA) is known to cause hyperammonemia.
- The precise mechanisms underlying VPA-induced hyperammonemia require further elucidation.
Purpose of the Study:
- To investigate the role of hepatic and renal systems in VPA-induced hyperammonemia following an amino acid load in rats.
Main Methods:
- Rats were administered valproic acid (VPA) and an amino acid load.
- Arterial ammonia levels were measured.
- Nephrectomized rats were used to assess renal contribution.
- Hepatic mitochondrial carbamyl phosphate synthetase I activity was measured.
Main Results:
- VPA administration consistently elevated arterial ammonia in rats receiving an amino acid load.
- Hyperammonemia was dose-dependent on VPA and amino acid levels.
- Nephrectomized rats showed significant hyperammonemia, indicating a limited role for kidneys.
- VPA markedly reduced hepatic mitochondrial carbamyl phosphate synthetase I activity.
Conclusions:
- VPA-induced hyperammonemia is primarily due to the inhibition of hepatic intramitochondrial citrullinogenesis.
- The kidneys contribute minimally to the hyperammonemia observed after VPA administration.