Choong-Yong Kim

Effects of Repeated Seafood Consumption on Urinary Excretion of Arsenic Species by Volunteers

Arsenic (As) is a known human carcinogen and widely distributed in the environment. The main route of As exposure in the general population is through food and drinking water. Seafood harvested in Korea contains high-level organoarsenics such as arsenobetaine, arsenocholine, and arsenosugars, which are much less harmful than inorganic arsenics. However, for those who eat large amounts of seafood it is important to understand whether seafood consumption affects urinary levels of inorganic As metabolites such as arsenite, arsenate, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). In this study we investigated urinary As metabolites (inorganic As, MMA[V], DMA[V]) and some biological indexes such as AST, GSH, GPX, lipid peroxidation, and uric acid in volunteer study subjects (seven males and nine females). Total urinary As metabolites were analyzed by the hydride generation method, followed by arsenic speciation using HPLC with ICP-mass spectrometry. Study subjects refrained from eating seafood for 3xa0days prior to the first urine collection and then ingested seafood daily for 6 consecutive days. The first voided urine of the morning was collected from each subject the first day of the consecutive 6xa0days of seafood ingestion but prior to the first seafood meal. The first voided urine of the morning was also collected on days 1, 2, 3, 4, 5, 6, 7, 10, and 14 after seafood ingestion. The daily mean intake of total As was 6.98xa0mg, comprised of 4.71xa0mg of seaweed (67%), 1.74xa0mg of flat fish (25%), and 0.53xa0mg of conch (8%). We observed a substantial increase in total urinary As metabolites for subjects consuming seafood from day 1, which recovered to control level at day 10. The increase in total urinary As metabolites was attributed to the increase in DMA, which is a more harmful metabolite than organoarsenics. However, no significant changes in response biological indexes were observed. These results suggest that it is necessary to evaluate As metabolism when assessing the exposure to inorganic As and potential chronic health effects of seafood consumption in Korea.

Simultaneous gene expression signature of heart and peripheral blood mononuclear cells in astemizole-treated rats.

We investigated the effects of astemizole, a second-generation antihistamine, on the heart and peripheral blood mononuclear cells (PBMCs) and identified the early markers of its cardiotoxicity using gene expression profiling. Astemizole causes torsades de pointes, which is a type of ventricular tachycardia. We administered astemizole (dosage: 20, 60xa0mg/kg) to male Sprague–Dawley rats, using an oral gavage. Cardiac tissue and PBMCs were collected from the rats 4xa0h after treatment. Gene expression profiles were obtained using an Affymetrix GeneChip. The most deregulated genes were associated with energy metabolism pathways and calcium ion homeostasis in the heart of astemizole-treated rats. The most altered genes in the PBMCs were those involved in developmental processes and cardiotoxicity. Genes related to the response to oxidative stress, reactive oxygen species, heat shock proteins, hypoxia, immunity, and inflammation were also deregulated in the heart and PBMCs. These data provide further insight into the genetic pathways affected by astemizole. In addition, the simultaneously deregulated genes identified herein may be further studied. It will be interesting to find out whether single genes or certain sets of these genes could finally serve as biomarkers for cardiotoxicity of astemizole or other similar antihistamine drugs.

Toxicity Screening of Single Dose of Inorganic and Organic Arsenics on Hematological and Serum Biochemical Parameters in Male Cynomolgus Monkeys

A screening study of the acute toxicity of organic arsenics such as arsenobetaine and arsenocholine, a product of arsenic methylation metabolite, and inorganic arsenic was carried out to examine hematological and serum biochemical parameters in cynomolgus monkeys (Macaca fascicularis). We found soft and liquid feces, and vomiting in all treated groups with inorganic and organic arsenics. The monkeys in inorganic arsenic-treated group showed a significant increase in vomiting frequency compared with those in three organic arsenics-treated groups. These results suggest that inorganic arsenic might be more toxic than three other organic arsenics tested. The monkeys in inorganic arsenic-treated group showed a decrease in platelet and an increase in monocyte on day 4 and the monkeys in arsenocholine-treated group showed an increase in reticulocyte percentage on day 8. The monkeys in inorganic-treated group also showed decreases in AST and ALT values and the monkeys in arsenobetaine-treated group showed a decrease in AST value and an increase in T-CHO value. However, these hematological and biochemical changes were within the physiological ranges, showing that the single dose of inorganic and organic arsenics did not affect at least hematological and serum biochemical parameters. The present study of toxicity with single dose of arsenics provides valuable indicators for longer term study of toxicity of repeated doses of arsenics in primates.

Quantification of oltipraz using liquid chromatography–tandem mass spectrometry and its application to a pharmacokinetic study in rat plasma

An assay method for the determination of oltipraz, a candidate drug for the treatment of liver fibrosis and liver cirrhosis, was developed in rat plasma using a fast-flow protein precipitation (FF-PPT) method coupled with LC-MS/MS for quantification to reduce the labor and to improve the speed of analysis. The applicability of the assay to pharmacokinetic studies was also evaluated. Oltipraz and ethyl-oltipraz, an internal standard (IS), were analyzed by multiple reaction monitoring (MRM) at m/z transitions of 227→193 and 241→174, respectively. A lower limit of quantification (LLOQ) of 20 ng/mL was observed, with a linear dynamic range from 20 to 4000 ng/mL (R>0.997). The accuracy, precision, dilution, recovery, and stability of the assay were deemed acceptable according to FDA guidelines. Oltipraz concentrations were measured successfully in plasma samples up to 12h post-dose in rats that had received an oral dose of 60 mg/kg. The findings indicate that the assay method is rapid and sensitive to oltipraz, showing applicability for pharmacokinetics (PK) studies of oltipraz in other small animals, including rats.

The stoichiometric relationship between KCNH-2 and KCNE-2 in IKr channel formation ☆

KCNH-2 and KCNE-2 may encode the channel-forming alpha- and regulatory beta-subunits, respectively, of I(Kr) channels, which are involved in inherited or acquired long QT syndrome. However, in contrast to other multimeric channels, the stoichiometry of KCNH-2 and KCNE-2, which should be reasonably maintained if they are to be accepted as the components of a multi-molecular complex, has not been established, yet. In this study, we found that the protein expression of KCNE-2 was adequate to support the formation of a complex with KCNH-2; however, the level of transcription was not. This finding, together with previous data from electrophysiological and molecular biological studies, supports that KCNH-2 and KCNE-2 are molecular components of I(Kr) channels.

QUANTIFICATION OF ZABOFLOXACIN IN RAT PLASMA USING HPLC-UV DETECTOR AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

This paper presents a simple, rapid, and sensitive method of investigating the pharmacokinetics of zabofloxacin, a fluoroquinolone antibiotic agent used to treat infections caused by multidrug-resistant Gram-positive pathogens. The method presented involves the use of high-performance liquid chromatography with ultraviolet (UV) detection without an internal standard. Zabofloxacin was separated using an isocratic elution on a Capcell Pak C18 column using an acetonitrile–methanol–phosphate buffer (1 g of KH2PO4 and 1 g of heptane sulfonic acid sodium salt in 720 mL of purified water) and a 1 M tetrabutylammonium dihydrogenphosphate solution (18.5:8.5:72:1, by volume) as a mobile phase at a flow rate of 0.25 mL/min with UV detection at 275 nm. The lower limit of quantification (LLOQ) and the upper limit of quantification (ULOQ) were 100 ng/mL and 20000 ng/mL, respectively, with acceptable linearity in the range from 100 to 20000 ng/mL (R > 0.999). The intra- and inter-day accuracy (RE) ranged from −8.2% to 1.8% and the intra- and inter-day precision (CV) ranged from 3.8% to 10.6% for zabofloxacin. In addition, stock solution stability, recovery, freeze–thaw effects, and short-term and long-term stability met the acceptance criteria. Following oral administration of zabofloxacin to rats at a dose of 250 mg/kg, the concentration of zabofloxacin was readily quantifiable in plasma samples up to 8 hr post-dose. This suggests that a validated assay can be used to study the pharmacokinetics of zabofloxacin in rats.