Urinary excretion of mercapturates as a biological indicator of exposure to electrophilic agents

The urinary excretion of mercapturates was followed photometrically in individuals exposed to styrene, a mixture of aromatic hydrocarbons, butadiene, vinyl chloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, 1,1,1-trifluoro-2-bromo-2-chloroethane (Halothane), ethylene oxide, epichlorhydrin, bis(chloromethyl)-ether, N-methylacrylamide, dimethylformamide, nitrosamines or cis-platinum and in groups of controls, smokers and nonsmokers, males and females, the residents of city P, industrial town V.M. and mountain village S. The increase in the urinary excretion of mercapturates was found in individuals exposed to styrene, aromatic hydrocarbons, dimethylformamide, 1,1,1-trichloroethane, and in smokers. In groups of controls, the lowest mercapturate concentrations were detected in the urine samples of nonsmokers from the mountain village S. where the degree of air pollution due to motor vehicle emissions was lowest at the time of investigation.     

Urinary excretion of and recent N-6-3 fatty acid intake

Epidemiological studies were performed in a Japanese fishing village when catches of fish were highest and in a Japanese farming village with usual fish consumption. Intake of eicosapentaenoic, docosahexaenoic and also arachidonic acid were significantly higher in the fishing village during the 3 days of the study than in the farming village. The correlation between eicosapentaenoic acid intake on the day when urine was collected and excreion of Δ 17-2,3-dinor-6-keto-prostaglandin F_1α, the main urinary metabolite of prostaglandin I₃, was highly significant, whereas there was no correlation between arachidonic or linoleic acid intake and excretion of 2,3-dinor-6-keto-prostaglandin F_1α, the main urinary metabolite of prostaglandin I₂. We suggest that the arachidonic acid pool for prostaglandin I₂ production is not quickly influenced by dietary linoleic or arachidonic acid because of a large pool size of arachidonic acid and a slow conversion of linoleic acid to arachidonic acid, while prostaglandin I₃ formation is directly related to the intake of eicosapentaenoic acid.     

用阳离子交换树脂测定尿三甲基组氨含量

因3-甲基组氨酸(3MH)从肌肉蛋白降解后,不重新参加蛋白质的合成,而从尿中排出,所以把它作为肌肉蛋白质分解的可靠指标。本文以Radha和Bess-man在1982年建立,Fitch等在1986年改进的阳离子交换树脂法。以大部国产试剂,对柱长、内径、pH等作了适当的改进,得到了满意的测定3MH的结果。从0.15到1.0μMol的三点标准曲线与Fitch等的相似,此法重复性好,回收率高,测定范围广,是较为简单,可推行的方法。用此法测定了烧伤和正常鼠尿3MH的含量,烧伤组14.5%Cv和对照组13.0%Cv,显示大鼠每天尿中排出的3MH含量比较稳定,说明烧伤和正常鼠肌肉蛋白质的分解比较恒定。烧伤组鼠尿3MH的每天排出量高于正常组35%以上,表明烧伤鼠肌肉蛋白质的分解速率高于对照组。     

Measurement of urinary 3-methylhistidine with cationic-exchange resin

A simple method is presented for measurement of urinary 3-methylhistidine (3MH) using a cationic exchange resin treatment followed by colorimetric analysis. Equations are given to correct for the interference by histidine (4.3% by mole) in the colorimetric analysis. This correction is especially important for measurement of urinary 3MH in pregnant women or in other subjects with elevated histidine excretion. Good recovery of added standard and good reproducibility of results are documented. Preliminary data from a study of pregnant women are reported, suggesting an increased excretion of 3MH during pregnancy. Large day-to-day variability of 3MH excretion was observed within subjects. It is recommended that repeated measurements be done on each subject when determining 3MH excretion.     

Quantitative gas chromatographic determination of 3-methylhistidine in biological fluids

The gas chromatographic procedure is suggested to determine 3-methylhistidine in biological fluids. The amino acid fraction containing 3-methylhistidine is separated by ion-exchange chromatography. Amino acids are transformed into N-trifluoroacetyl-O-isobutyl esters which are analyzed by the gas chromatography instrument with micropacked columns and ionization-resonance detector. The limit of the quantitative determination of 3-methylhistidine is 50 ng per a probe.     

Urinary excretion of dimethylarginines in premature infants

Urinary excretion of NG,N'G-dimethylarginine (NG,N'G-Me2Arg) and NG,NG-dimethylarginine (NG,NG-Me2Arg) was measured in premature infants. The NG,N'G-Me2Arg/NG,NG-Me2Arg ratio was much higher in newborn infants than in older children or adults. Linear regression analysis showed a significant negative correlation between the degree of maturity and the excretion of NG,N'G-Me2Arg. A significant direct linear relationship also was found between the excretion of NG,N'G-Me2Arg and the rate of whole body nitrogen flux and of protein synthesis and catabolism. No correlation was found between the excretion of the dimethylarginines and 3-methylhistidine, but the dimethylarginine/3-methylhistidine ratio declined with advancing conceptual age. A direct linear relationship was found between excretion of NG,N'G-Me2Arg and NG,NG-Me2Arg and whole body nonskeletal muscle protein breakdown. No correlation was found between nonskeletal muscle protein catabolism and 3-methylhistidine excretion. We estimate that approximately 0.34 mumole of dimethylarginine are excreted per gram of nonskeletal muscle protein catabolized. Dietary intake did not affect the excretion of either NG,N'G-Me2Arg or NG,NG-Me2Arg. The data suggest that measurement of urinary dimethylarginines might be useful in the nutritional assessment of premature infants.     

Quantitation of urinary 3-methylhistidine excretion in growing dogs as an index of in vivo skeletal muscle catabolism

Purpose: To quantitate urinary 3-methylhistidine (3-mh) excretion as an index of in vivo muscle catabolism in dogs fed diets containing either normal or high protein levels.Methods: Twelve male, 5-month-old Beagle dogs were housed individually in metabolism cages and fed a non-meat, purified diet. They were divided into two diet groups of six dogs each, receiving 22.6% (NP) or 41.1% (HP) DM crude protein, respectively. Three dogs from each group received an intravenous injection of 385 +/- 29 kBq [14C] 3-mh. HCl. Urine and feces were collected daily until radioactivity returned to background levels (17 days). Urinary 3-mh was measured using an amino acid analyzer and percentage of bound 3-mh was estimated via acid hydrolysis.Results: Results are reported as means +/- SEM. 3-mh recovery in urine and feces of dogs were 263 +/- 28 kBq and 50.7 +/- 2.2 kBq and 327 +/- 45 kBq and 25.9 +/- 25.9 kBq for the NP and HP groups, respectively. The total cumulative 3-mh recoveries for the NP and HP groups were 81.8% +/- 2.8 and 91.4% +/- 2.7, respectively. Bound 3-mh accounted for 2.1 to 4.8% of urinary 14C-3-mh.Conclusions: Growing Beagle dogs excrete a higher percentage of 3-mh in feces (13.5% vs. 6.7%) when consuming the NP versus the HP diet. It appears that some of the 14C was lost in CO(2) and/or re-circulated in the body, as reported for sheep and pigs. We conclude that urinary 3-mh does not appear to be a quantitative index of in vivo muscle catabolism in growing dogs.