Association of UGT1A1 Gly71Arg with urine urobilinogen.

Bilirubin is glucoronized by uridine diphosphate-glucuronosyl transferase 1A1 (UGT1A1) mainly in the liver, and excreted into bile. The conjugated form is metabolized into the unconjugated form, and then into urobilinogen by bacteria in the intestine. Unconjugated bilirubin and urobilinogen are absorbed into the blood stream. The kidney filtrates conjugated bilurubin and urobilinogen into urine. Accordingly, the reduced enzyme activity of UGTIAI may decrease serum conjugated bilirubin levels, resulting in a lower frequency of positive results of urine bilirubin and urobilinogen. This study examined the associations of UGTIAI Gly71Arg (UGTIAI *6) with urine bilirubin and urobilinogen, as well as serum AST, ALT and GGT. Subjects were 5,172 inhabitants 35 to 69 years old who participated in a cohort study in Nagoya from June 2008 to May 2010. Among them, data from 5,151 participants (1,465 males and 3,686 females) were available for analysis. The age-sex-adjusted odds ratio (OR) of ArgArg relative to GlyGly was 1.37 (95% confidence interval (95% CI), 0.55-1.23) for bilirubin, and 1.67 (95% CI, 0.86-3.26) for urobilinogen. Those of ArgArg+ArgGly were 0.87 (95% CI, 0.59-1.27) and 1.50 (95% CI, 1.17-1.94), respectively. AST, ALT and GGT levels had no associations with the genotype. Although the significant association for urobilinogen was contrary to the biological expectation, this study indicated that UGTIA1 Gly71Arg may be a genetic factor of urine urobilinogen.

Effect of DDVP on urinary excretion levels of pyrethroid metabolite 3-phenoxybenzoic acid in rats.

Pyrethroid insecticide (PYR) is used worldwide in agriculture and for indoor extermination of harmful insects. Urinary PYR metabolites (e.g. 3-phenoxybenzoic acid, 3PBA) have been used as the most sensitive biomarker for environmental PYR exposure since the late 1990s. In this study, we examined the effect of organophosphorus insecticide (OP) dichlorvos (DDVP) on excretion levels of urinary cis-permethrin-derived 3PBA in rats. Concentration of urinary 3PBA and cis-permethrin in plasma was monitored using gas chromatography-mass spectrometry and high-performance liquid chromatography after cis-permethrin injection (20 mg/kg) via the tail vein of rats pretreated intraperitoneally with DDVP (low dose, 0.3 mg/kg; high dose, 1.5 mg/kg). The amount of urinary 3PBA excretion over 48 h after cis-permethrin administration in control was 21.5±5.1 µg (mean±S.D.). In the low- and high-dose DDVP groups, the amounts of urinary 3PBA excretion were decreased to 81.1% (17.4±2.7 µg) and 70.3% (15.1±2.6 µg) of control, respectively. The plasma concentrations of cis-permethrin-derived 3-phenoxybenzyl alcohol (3PBAlc), which is a metabolite derived following hydrolysis of cis-permethrin, in high-dose DDVP group (0.18±0.01 µg) were significantly lower than in control (0.23±0.03 µg) 1h after cis-permethrin injection. Both in the control and high-dose DDVP group, no differences were observed in the excretion levels of urinary 3PBA after injection of 3PBAlc (25mg/kg, i.v.). These results suggested that the effect of DDVP on the amount of urinary 3PBA excretion was caused by the DDVP-induced modification of the cis-permethrin metabolic pathway. In conclusion, the possible decrease in urinary excretion level of 3PBA due to co-exposure to OPs should be considered in the biological monitoring of PYR exposure.

Toxicokinetics of pyrethroid metabolites in male and female rats.

The toxicokinetic characteristics of 3-phenoxybenzyl alcohol (3PBAlc) and 3-phenoxybenzaldehyde (3PBAld; metabolites of pyrethroid [PYR] after 25mg/kg, single intravenous administration), were investigated in male and female rats. The systemic clearance (Cl) of 3PBAlc in females (0.403±0.040l/h/kg) was significantly larger than that of males (0.227±0.036l/h/kg). The plasma concentration-time curve of 3PBAld decreased gradually and then increased again 1 and 2h after injection, suggesting the effect of enterohepatic circulation. The present study characterized the elimination and distribution of PYR metabolites and suggests that gender-related difference exists in the toxicokinetics of 3PBAlc and 3PBAld in rats.