A selective method for determination of methylguanidine in biological fluids. Its application in normal subjects and uremic patients.

A selective analytical method for the determination of methylguanidine in plasma in biological fluids has been developed. Methylguanidine is extracted in a column to dichloromethane as an ion pair with hexanitrodiphenylamine (dipicrylamine). It is isolated from coextracted compounds by partition chromatography as the picrate ion-pair. The methylguanidine fraction is collected and after reextraction to a buffer solution the methylguanidine content is quantitatively determined photometrically as picrate. An absolute recovery of 95 +/- 5% was obtained in the concentration range 1.5-10 microgram/ml plasma. The concentration of methylguanidine in plasma was higher in uremic patients, (44.4 +/- 5.71 mumol/l in conservatively-treated and 42.4 +/- 7.87 mumol/l in dialysis-treated patients) than in normal subjects, (4.0 mumol/l), but still lower than reported by other investigators using non-specific methods and also lower than the concentrations found to be toxic in experimental animals. There was a significant correlation between methylguanidine and creatinine concentration but no correlation between methylguanidine and urea concentration in plasma. No obvious relation was found between plasma methylguanidine concentration and various uremic symptoms, mode of treatment or protein intake.