Sandra Evans

Early changes in hepatic redox homeostasis following treatment with a single dose of valproic acid

Changes in reduced glutathione (GSH) and pyridine nucleotide phosphate levels as well as in the activities of the glutathione peroxidase-reductase system and glucose-6-phosphate dehydrogenase have been studied in rats after a single i.p. administration of various doses of valproic acid (VPA). GSH level decreased in a dose-dependent relation. At the end of 180 min GSH levels either returned to control limits (lower doses) or showed a tendency to normalize (higher doses). GSH loss was paralleled by the reduction in glutathione reductase activity. A significant NADPH reduction was also seen after animal exposure to high VPA doses. At the end of 180 min a maximal NADPH decrease was reached. The activities of both glutathione peroxidase and glucose-6-phosphate dehydrogenase were suppressed irrespective of whether animals were given low or high VPA doses.

Neurophysiological and biochemical changes evoked by valproic acid in the central nervous system.

(1) Valproic acid is an anticonvulsant agent widely used in the management of various forms of epilepsy, including absence, myoclonic and tonic-clonic seizures. (2) It also has anticonvulsant potency in a wide variety of animal models of epilepsy. (3) This action is generally thought to be exerted through modulation of the activity of the endogenous inhibitory neurotransmitter, gamma-aminobutyric acid. (4) Evidence that valproic acid interacts with the gamma-aminobutyric acid system is presented. (5) Interactions of valproic acid with other neurotransmitters, i.e. aspartate, glutamate, taurine, serotonin, as well as with cyclic nucleotides and hormones are also considered. (6) Direct effects of valproic acid on excitable membranes and its relationships with analgesia are outlined.

Early postmenopausal bone loss in hyperthyroidism

OBJECTIVES To evaluate the effect of hyperthyroidism on bone in relation to the menopausal state. METHODS Fifty-nine hyperthyroid (HYPER), 40 hypothyroid (HYPO), and 51 control euthyroid (EUTH) women were studied. Bone mineral density (BMD) was assessed by dual X-rays absorptiometry (DXA) at the lumbar spine, and at the femoral neck. A multi-site QUS device evaluated speed of sound (SOS) at the radius (RAD), tibia (TIB), metatarsus (MTR), and phalanx (PLX). Bone markers used were serum bone specific alkaline phosphatase (BSAP) and urinary deoxypyridinoline (DPD). RESULTS At all sites, SOS was lower in HYPER than in EUTH (RAD P<0.05, TIB P<0.01, MTR P<0.05, PLX P=0.01). The low SOS was only noted at the early postmenopausal period. BMD at the femoral neck but not at the lumbar spine was lower in HYPER as compared to EUTH (P<0.05). Both femoral neck and tibia were the sites with the highest odds ratio for being hyperthyroid (2.3 and 2.04, respectively). There was no correlation between BMD or SOS and FT(4), TT(3) or duration of hyperthyroidism. BSAP and DPD positively correlated with FT(4) and TT(3) (P<0.05). CONCLUSIONS This study suggests that hyperthyroidism affects bone mineralization especially during the early postmenopausal period, and the effect is mainly at the cortical bone.

Prevalence of celiac antibodies in children with neurologic disorders

Neurologic complications are a recognized but unusual manifestation of celiac disease (CD) in adults and children. The use of antigliadin and antiendomysial antibodies in screening has revealed the frequency of CD among symptom-free individuals to be high. Recently, a high frequency (57%) of antigliadin antibodies was demonstrated in adult patients with neurologic dysfunctions of unknown cause. We investigated the yield of screening for CD in children with common neurologic disorders. One hundred sixty-seven children, 1-16 years of age, were included in the study: 41 with migraine headaches, 39 with attention-deficit disorder with or without hyperactivity, 36 with epileptic disorders, and 51 with hypotonia and motor abnormalities. Positive IgG antigliadin antibodies were evident in 22 children (13%) in the study group compared with three children (9%) in the control group. However, in all children, negative IgA and endomysial antibodies were observed; thus duodenal biopsies were not performed. Contrary to studies performed in adults, these results did not demonstrate any relationship between common neurologic disorders without a specific diagnosis during childhood and CD. Thus screening for CD does not need to be routinely included in the diagnostic evaluation of children with these disorders.

Inhibition of human red blood cell glutathione reductase by valproic acid

Glutathione reductase (GR) one of the enzymes of the glutathione redox cycle, plays a salient role in maintaining appropriate cellular levels of reduced glutathione. The enzyme in human red blood cells is inhibited in vitro by the anticonvulsant drug valproic acid (VPA). The inhibition is dose-dependent, reversible, uncompetitive and does not depend on the redox state of the enzyme. VPA also inhibits red blood cell GR activity in children being treated with the drug. The level of serum VPA correlates significantly with the suppression of GR activity.

Bone mineral density and turnover in children with attention-deficit hyperactivity disorder receiving methylphenidate.

Attention-deficit hyperactivity disorder (ADHD) is the most common behavior disorder among children; methylphenidate is a drug frequently prescribed for the control of its symptoms. One of the potential side effects of methylphenidate that concerns parents is its impact on the growth of children, since the mechanism by which methylphenidate might influence growth is not known. As linear growth is associated with an increase in bone mineral density and turnover, this study was undertaken to evaluate bone mineral density by dual photon absorptiometry and bone turnover by measuring serum bone-specific alkaline phosphatase and the urinary deoxypyridinoline excretion rate in children treated with methylphenidate for 1 to 2 years as compared to a control group. There were no significant differences in bone mineral density at either the lumbar spine or femoral neck in the study group (0.662 ± 0.04 and 0.735 ± 0.07 g/cm2, respectively) as compared to the controls (0.675 ± 0.05 g/cm2 and 0.734 ± 0.07 g/cm2, respectively). Furthermore, there were no significant differences in serum bone-specific alkaline phosphatase in the study group (58 ± 22 U/L) as compared to the control children (71 ± 34 U/L) or in urinary deoxypyridinoline in the study group (34 ± 38 nM/mM), as compared to the control group (27 ± 12 nM/mM). In conclusion, our data do not support a significant effect of methylphenidate on bone mineral density turnover in children when used for 1 to 2 years. (J Child Neurol 2000;15:436-439).

ERYTHROCYTE NA+, K+ AND CA2+, MG2+-ATPASE ACTIVITIES IN HYPERTENSIVES ON ANGIOTENSIN-CONVERTING ENZYME INHIBITORS

OBJECTIVE To investigate erythrocyte membrane Na+, K(+)- and Ca2+, Mg(2+)-ATPase activities in newly diagnosed hypertensive patients before and after 2, 4, and 6 months of treatment with enalapril or captopril as monotherapy. METHODS AND RESULTS Na+, K(+)-ATPase activity (nmol ATP hydrolysed/min per mg protein) rose by 6 months of treatment in both groups when values were compared in each treated group over time (4.5 +/- 0.8 to 9.9 +/- 1.2; 4.9 +/- 0.8 to 10.5 +/- 1.7, respectively, p < 0.001 for both). When the treated groups were compared with controls at each period of time, Na+, K(+)-ATPase activity was higher at months 4 and 6 (p < 0.001) for both groups, respectively). Ca2+, Mg(2+)-ATPase activity (nmol ATP hydrolyzed/min per milligram protein) in the absence and in the presence of calmodulin increased in the enalapril (6.4 +/- 0.7 to 8.9 +/- 0.95, p < 0.05; 13.4 +/- 1.2 to 17.2 +/- 1.2, p < 0.05, respectively) and captopril (7.0 +/- 0.6 to 8.5 +/- 0.7; 14.4 +/- 1.1 to 16.0 +/- 1.0, p < 0.05, respectively) groups after 6 months of treatment compared within each treated group over time. When patient groups were compared with controls at time 0, 2, 4, and 6 months, the pump activity was higher in the treated groups at 6 months. CONCLUSION The long-term enhancement of cell membrane Na+, K(+)-and Ca2+, Mg(2+)-ATPase activity associated with enalapril and captopril therapy may represent a specific effect of these agents or alternatively, a nonspecific outcome of blood pressure reduction.

Oral N-acetylcysteine has a deleterious effect in acute iron intoxication in rats.

Acute iron intoxication is associated with depletion of reduced glutathione in hepatocytes and changes in the glutathione system enzymes. We hypothesized that treatment with N-acetylcysteine (NAC), a glutathione reducing agent and an antioxidant, would reduce mortality in acute iron intoxication. We used a rat model to test this hypothesis. Male rats were assigned to 4 groups. Group 1 received 400 mg/kg elemental iron by oral gavage, group 2 received the same dose of iron followed by NAC, group 3 received NAC only, whereas group 4 received distilled water. Iron and liver transaminases in the blood, and glutathione system enzymes in the liver and erythrocytes were measured. Mortality in group 2 was significantly higher after 2, 6, and 24 hours compared with group 1 (P < .001). No deaths were observed in groups 3 and 4. Serum iron levels were significantly higher in group 2 rats compared to group 1 rats (P < .001). Hepatic and erythrocyte glutathione system enzymes were significantly lower among rats in group 2 compared to rats in group 1. The administration of NAC probably increased the absorption of iron through the gastrointestinal tract, causing higher serum iron levels with significant hepatic damage. These results indicate that in a rat model of acute iron intoxication, orally administered NAC may increase mortality.

Effect of sodium valproate on subcellular fraction enzymes in rat liver.

Previous observations that valproic acid (VPA) causes hepatic damage prompted us to investigate the effect of large doses of the drug (0.6, 1.2 and 1.8 mmol/kg/day) on a number of liver enzymes located on different subcellular fractions. In mitochondria, glutamate dehydrogenase, aspartate aminotransferase and ornithine carbamoyltransferase were significantly increased (1.8 mmol/kg/day). In microsomes, gamma-glutamyltransferase activity increased significantly (1.8 mmol/kg) and cytochrome P-450 content decreased significantly (1.2 and 1.8 mmol/kg). In cytosol, both aspartate and alanine aminotransferase activities were increased at all dose levels. These results indicate that VPA induces dose-dependent changes in some liver enzyme activities.

Erythrocyte Na+,K+-ATPase and nasal potential in pseudohypoaldosteronism*

objectives Pseudohypoaldosteronism type 1 (PHA1) is a rare inherited disorder characterized by salt‐wasting due to target organ unresponsiveness to mineralocorticoids. PHA1 comprises two clinically and genetically distinct entities; isolated renal and systemic forms.