PT  - JOURNAL ARTICLE
AU  - Silva, Margarida F. B.
AU  - IJlst, Lodewijk
AU  - Allers, Paul
AU  - Jakobs, Cornelis
AU  - Duran, Marinus
AU  - de Almeida, Isabel Tavares
AU  - Wanders, Ronald J. A.
TI  - VALPROYL-DEPHOSPHOCoA: A NOVEL METABOLITE OF VALPROATE FORMED IN VITRO IN RAT LIVER MITOCHONDRIA
AID  - 10.1124/dmd.32.11.1304
DP  - 2004 Nov 01
TA  - Drug Metabolism and Disposition
PG  - 1304--1310
VI  - 32
IP  - 11
4099  - http://dmd.aspetjournals.org/content/32/11/1304.short
4100  - http://dmd.aspetjournals.org/content/32/11/1304.full
SO  - Drug Metab Dispos2004 Nov 01; 32
AB  - The mitochondrial metabolism of valproic acid (VPA) was investigated in vitro to elucidate its β-oxidation pathway since the characterization of VPA intermediates in the acyl-CoA thioester form, and not just in their free acid form, has not been fully achieved. Intact rat liver mitochondria were incubated with [4,5-3H2]VPA and [2-3H]VPA. The respective intermediates, valproyl-CoA, Δ2(E)-valproyl-CoA, 3-hydroxyvalproyl-CoA, and 3-oxovalproyl-CoA were analyzed by reverse phase high performance liquid chromatography (HPLC) with radioisotope and UV detection. An unknown metabolite, originating from both labeled substrates, was detected. It was identified as valproyl-dephosphoCoA (valproyl-dephCoA) by fast atom bombardment mass spectrometry (FAB-MS) analysis of the corresponding HPLC peak fraction. The FAB-MS spectrum of the authentic chemically synthesized valproyl-dephCoA proved to be consistent with that of the unknown compound. Valproyl-dephCoA is produced from valproyl-CoA in mitochondria, probably via a phosphatase-catalyzed reaction. This conversion was shown to be more dependent on the energy state involving [AXP] ([AXP] = [ATP] + [ADP] + [AMP]) and [phosphate] concentrations rather than the strict mitochondrial [ATP]/[ADP] ratio. The results indicate that higher concentrations of AXP and phosphate inhibit the dephosphorylation of valproyl-CoA. A complete understanding of the toxic significance of valproyl-dephCoA formation in vivo as a potential inhibitor of fatty acid β-oxidation is important to clarify the pathogenesis of VPA-associated hepatotoxicity. The American Society for Pharmacology and Experimental Therapeutics