Inhibitory effect of valproate on weak organic acid uptake in rat renal proximal tubules

Case report: valproic Acid and risperidone treatment leading to development of hyperammonemia and mania

This case report describes two children who developed hyperammonemia together with frank manic behavior during treatment with a combination of valproic acid and risperidone. One child had been maintained on valproic acid for years and risperidone was added. In the second case, valproic acid was introduced to a child who had been treated with risperidone for years. In both cases, discontinuing the valproic acid resulted in normalization of ammonia levels and cessation of the manic behavior. This case report alerts physicians to the importance of obtaining serum ammonia levels in children treated with valproic acid and risperidone who present with manic behavior.

Effects of valproic acid on cardiac metabolism

We investigated whether the antiepileptic valproic acid (VPA) might interfere with oxidative metabolism in heart, as it does in liver. We administered VPA to working rat hearts perfused with radiolabeled carbohydrate and fatty acid fuels. Measurements included oxidation rates of (i) glucose, pyruvate, or lactate in the presence of palmitate and (ii) palmitate, octanoate, or butyrate in the presence of glucose. Oxidation rates were quantified as the rate of appearance of 14CO2 or 3H2O from 14C- or 3H-labeled substrates. In hearts perfused with palmitate, VPA (1 mmol/L) strongly inhibited the oxidation of pyruvate and lactate but slightly stimulated the oxidation of glucose. VPA also inhibited lactate or pyruvate uptake into erythrocytes in vitro. In hearts perfused with glucose, VPA strongly inhibited the oxidation of palmitate and octanoate but had no effect on butyrate oxidation. The absence of valproate CoA ligase activity in cell-free homogenates indicated that the inhibition of fatty acid oxidation by VPA did not require prior activation to valproyl-CoA. The results are consistent with the hypothesis that VPA selectively interferes with myocardial fuel oxidation by mechanisms that are independent of conversion to the CoA thioester.

Molecular and cellular physiology of renal organic cation and anion transport

Organic cations and anions (OCs and OAs, respectively) constitute an extraordinarily diverse array of compounds of physiological, pharmacological, and toxicological importance. Renal secretion of these compounds, which occurs principally along the proximal portion of the nephron, plays a critical role in regulating their plasma concentrations and in clearing the body of potentially toxic xenobiotics agents. The transepithelial transport involves separate entry and exit steps at the basolateral and luminal aspects of renal tubular cells. It is increasingly apparent that basolateral and luminal OC and OA transport reflects the concerted activity of a suite of separate transport processes arranged in parallel in each pole of proximal tubule cells. The cloning of multiple members of several distinct transport families, the subsequent characterization of their activity, and their subcellular localization within distinct regions of the kidney now allows the development of models describing the molecular basis of the renal secretion of OCs and OAs. This review examines recent work on this issue, with particular emphasis on attempts to integrate information concerning the activity of cloned transporters in heterologous expression systems to that observed in studies of physiologically intact renal systems.

Renal injury from valproic acid: case report and literature review

A child with developmental delay and epilepsy developed glucosuria approximately 16 months after starting valproic acid therapy. Laboratory evaluation revealed global defects in proximal tubule function consistent with the De Toni-Debré-Fanconi syndrome. Discontinuation of valproate led to complete recovery 5 months later. Review of previously reported cases indicates that this complication is unique to children and reversible when the medication is discontinued.