Distribution in Experimental Animal and Excretion of Labeled Ponceau MX-35S

Crystalline Ponceau MX (Ponceau R, disodium 1-(2, 4-xylylazo)-2-naphthol-3 , 6-disulphonate) labeled with 35S was synthesized from radioactive H2*SO4, β-naphthol and mxylidine, and a solution of the compound having the radioactivity of 5×105cpm/ml by gas flow counter was prepared. Then this solution was given to experimental animals to investigate the distribution and excretion of the dyestuff by measuring the radioactivity of internal organs, blood, feces and urine. The radioactivity of dry-powdered samples of these biological materials were measured by gas flow counter and calibrated for self-absorption. After peroral administration of the solution, the radioactivity was almost transferred from stomach to intestine in 3~6 hours, and disappeared from stomach in 24 hours after administration. Absorption to blood was relatively little, about 0.23% of dose was seen in total blood at 6 hours after administration, and the radioactivity disappeared from blood 6 hours later (Table 1). By peroal administration to rats, the highest accumulation of radioactivity was observed in liver, and secondly in kidney (Table 1). In the case of intravenous injection to rabbits, the same finding was noted (Table 2). After peroal administration to rats, the excretion of radioactivity was done mainly into feces and scarcely into urine (Table 1). After intravenous injection to rabbits, radioactivity-level in blood fell down quickly in 1 hour, and after that, it decreased gradually upto 5 hours later (Fig. 4). The radioactive substance was excreted mainly into urine in this case (Table 2). A part of urine excreted after intravenous injection to rabbit was developed by ordinary technique of paper chromatography with a mixture of acetone・isoamyl alcohol・ water (6:5:5) and one radioactive spot was obtained (Fig. 5). This spot was identified as one of unchanged Ponceau MX by comparing the paper chromatograms of standard Ponceau MX and 1-amino-R-acid (Fig. 6). It was presumed that about 50% of injected dose of Ponceau MX-35S was excreted without undergoing any metabolism in urine, by measuring the radioactivity of the chromatogram of urine (Fig. 5). (Received August 14, 1967) *国 立衛生試験所放射線化学部:東 京都世田谷 区玉川用賀町2-203