The analysis of urinary N-methylacetamide by GC-NPD with a direct injection / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To establish a method to detect N-methylacetamide (NMAC) concentration in urine of workers occupationally exposed to NMAC with directly injecting the sample into capillary gas chromatography.</p><p><b>METHODS</b>After frozen urine samples were isolated from precipitation by centrifugation, the aliquot of supernatant was pretreated by protein precipitation with dilution of methanol. The methanol supernatant was separated by Polyethylene Glycol (PEG) capillary columns and detected by nitrogen phosphorous detector (NPD).</p><p><b>RESULTS</b>Good linearity was obtained in the concentration range of 1.0 ∼ 250 mg/L. The correlation coefficient was 1.0000. The minimum detection limit of NMAC in urine was 0.2 mg/L. The method recovery rates were 96.0% ∼ 99.4% at three different concentrations. The mean recovery rate was 97.8%. The relative standard deviations (RSD) of intra- and inter-day were between 1.5% ∼ 3.4%.</p><p><b>CONCLUSION</b>The method was simple, rapid, selective and sensitive and was applicable to detect the urinary NMAC concentration for monitoring occupational exposure levels.</p>

Biological limit value for occupational exposure to N, N-dimethylacetamide / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To establish Biological Limit Value (BLV) for N, N-dimethylacetamide (DMAC).</p><p><b>METHOD</b>201 workers in 3 spandex factories exposed to DMAC were recruited. Air samples were collected using personal air samplers, and urine samples from each works were collected at the end of shift at end of workweek. The urinary metabolite NMAC and air samples of DMAC were determined by gas chromatography (GC). Percentile and relative internal exposure (RIE) were analyzed and proposed a BLV for DMAC.</p><p><b>RESULTS</b>The number of workers who exposure to DMAC below OELs were 133 (66.2%) among 201 workers monitored. Geometric mean (range) concentration of DMAC in air was 19.4 (0.40 ∼ 300.12) mg/m(3), and that of NMAC in urine was 23.7 (1.30 ∼ 189.42) mg/g Cr. A linear correlation was found between the personal air DMAC and creatinine-adjusted NMAC levels in urine collected at the end of shift at end of workweek (F = 188.872, R(2) = 0.487,P < 0.001). The relationship can be described by the equation Log (NMAC mg/g Cr) = 0.685 + 0.455 log (DMAC mg/m(3)). According to the equation the current China OELs value of 20 mg/m(3) would lead to a mean NMAC concentration of 18.92 mg/g Cr. The 90th percentile biomonitoring result below 20 mg/m(3) 8-hour TWA is 23.9 mg MMAC mg/g Cr, and that of NMAC in urine calculated by relative internal exposure (RIE) was 19.0 mg/g Cr.</p><p><b>CONCLUSION</b>A BLV of 20 mg/g Cr NMAC in urine at the end of shift at end of workweek for DMAC was recommend by reference to official values from other countries.</p>

Relationship between the increase of hepatic D-bifunctional protein activity and bile acid biosynthesis in rats / 中国医学科学院学报

<p><b>OBJECTIVE</b>To determine the physiological role of D-bifunctional protein (DBP) in bile acid biosynthesis through investigating the effect of increasing activity of DBP on bile acid biosynthesis.</p><p><b>METHODS</b>Twenty male Wistar rats were divided into two groups: diethylhexyl phthalate (DEHP) group (n = 10) and control group (n = 10). Serum triglyceride, total cholesterol, hepatic DBP activity, and fecal bile acids were assayed. The mRNA levels of hepatic peroxisome proliferator-activated receptor alpha (PPARalpha), DBP, and cholesterol 7alpha-hydroxylase (CYP7A1) were detected by RT-PCR.</p><p><b>RESULTS</b>Compared with control group, serum triglyceride level was decreased significantly and PPARalphamRNA level was increased significantly in DEHP group (P < 0.01). Together with a sharp induction of DBP mRNA expression and DBP activity in DEHP group (P < 0.01), the levels of CYP7A1 mRNA and fecal bile acids were significantly increased by 1.9 times and 1.6 times respectively compared to control group (P < 0.01). There was a significantly positive correlation between DBP mRNA level or DBP activity and CYP7A1 mRNA level (r = 0.89, P < 0.01; r = 0.95, P < 0.01).</p><p><b>CONCLUSION</b>The up-regulation of DBP mRNA and activity in liver can result in the increase in CYP7A1 mRNA expression and bile acid biosynthesis, suggesting that DBP may be involved in bile acid biosynthesis together with CYP7A1.</p>