On the Colorimetric Estimation of Guanidine Bases in Blood

In 1924 Tiegs reported a new color reaction for the guanidine bases.On the basis of this reaction Marston (1924) elaborated a reagent for the calorimetric estimation of guanidine bases in pure solution.This reagent consisted of an alkaline peroxide-ferrocyanide-nitroprusside mixture which is by no means specific for the guanidine bases.Uric acid, ammonia, and most reducing substances inhibit the color reaction.Creatine and creatinine produce a color with the reagent.A short time later Marston (1925) pointed out that in estimating the guanidine bases in tissues ammonia may be removed by permutit and uric acid by precipitation with silver lactate but no details of the method were given.Whitehorn (1923) had already shown, however, that permutit removes guanidine from an aqueous solution of guanidine hydrochloride, and Pfiffner and Myers (1926) observed that permutit also removes methylguanidine and as-dimethylguanidine from aqueous solution, although the removal is not quantitative.A study of the reagent was undertaken in this laboratory with the object of applying it to the cbloiimetric estimation of guanidine bases in blood.In a preliminary communication Pfiffner and Myers (1926) described a modified peroxideferrocyanide reagent which kept well and gave within 5 minutes a full color development and did not fade or become turbid for more than an hour.Weber (1927) described a reagent for the calorimetric estimation of guanidine bases in which he substituted potassium ferricyanide for the potassium ferrocyanide and hydrogen peroxide of Marston's reagent.This substitution doubled the sensitivity of the reagent to guanidine bases.Major and Weber (1927) applied the reagent to the calorimetric estimation of guanidine bases in blood, and have made several reports of their various observations dealing particularly with hypertension.In connection with observations on the retention of creatinine in nephri-