Uptake, distribution and metabolism of [14C]amaranth in the female rat

Abstract

Four female rats were dosed by gavage with [14C]amaranth (20 mg/kg). Total radioactivity was measured in blood samples taken at specific times over a 24-hr period. The change in blood radioactivity with time after dosing was fitted to a one-compartment mathematical model. The mean times taken to reach maximum concentration of radioactivity and for the decline to 50% of the maximum concentration were 4·2 and 12·5 hr, respectively. Subsequently, two groups of four female rats were dosed with [14C]amaranth (as above) and killed 4 and 12 hr after dosing. The distribution of14C-activity in various tissues was measured. Calculations of the mean 14C-activity indicated that 14·2% of the administered dose was retained by the rats in the 24-hr period. No radioactivity was detected in respiratory gases. Radioactivity was detected in stomach, large and small intestine, blood, bile, heart, kidney, liver and lung 4 and 12-hr after treatment, but after 24 hr 14C-activity was no longer detectable in the blood, bile or heart. Over the 24 hr following dosing, 65–86% of the given14C-activity was recovered in the faeces. Total recoveries of 14C-activity ranged from 80–94% of the dose Radioactive amaranth, naphthionic acid and as many as five unidentified products were detected in the gastro-intestinal tract contents, urine and faeces by thin-layer chromatography.