Author
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Yokoi, Katsuhiko |
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Submitted to: Biological Trace Element Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/22/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Excessive dietary sodium chloride is an important risk factor for essential hypertension; reduction of dietary sodium chloride is one of the most effective treatments of essential hypertension. It is not well established whether the harmful effect of sodium chloride is derived from sodium ions or chloride ions because of the technical difficulties in measuring the chloride concentration in biological samples. In animal studies, the volume of urine is low and the urinary chloride concentrations are lower compared to urine of humans who usually consume salt in their diets. Subsequently, investigations of excessive dietary salt were limited to sodium ions not chloride ions. There is a need to develop a sensitive method for the determination of chloride that is applicable to animal urine specimens. Thus, a method for measuring the chloride concentration in biological samples of rodents was developed. The urinary excretion rate of chloride was 23.6+/-9.3 umol/h (mean+/-SD, n = 8) and 126.2 +/- 28.0 umol/h (n = 8) for rats fed a normal diet (2.6 g NaCl/kg diet) and a high-salt diet (82.6 g NaCl/kg diet) for 70 days prior to urine collection, respectively. This method is appropriate for low concentrations of chloride in samples or when sample volume is limiting, as in many animal studies such as metabolic urine collection from rats. Technical Abstract: A colorimetric method is outlined for the determination of chloride ion in biological samples (blood serum, plasma and urine). The present method is based upon the quantitative reduction of free mercuric ions by chloride ions. Chloride ions form an in dissociable complex with mercuric ions. The remaining free mercuric ions form a purple complex with diphenylcarbazone with an absorption maximum at 550 nm. The reduction of color intensity at 550 nm is directly proportional to chloride concentration in the sample. The linear concentration range in the final reaction mixture was 0 to 100 uM with correlation coefficient = -0.9997. The coefficient of variation for 50 uM chloride ion in the final reaction mixture was 0.9% (n = 6). This method was applied to the measurement of urinary chloride excretion in experimental rats. During 16 h-urine collection, no food was given and rats had free access to purified water. Urinary excretion rate of chloride was 23.6+/-9.3 umol/h (mean+/-SD, n = 8) and 126.2 +/- 28.0 umol/h (n = 8) for rats fed a normal diet (2.6 g NaCl/kg diet) and a high-salt diet (82.6 g NaCl/kg diet) for 70 days prior to urine collection, respectively. This method is appropriate for low concentrations of chloride in samples or when sample volume is limiting, as in many animal studies such as metabolic urine collection from rats. |
