Determination of imidazole acetic acid and its conjugate(s) levels in urine, serum and tissues of rats: studies on changes in their levels under various conditions

Abstract

A convenient and reproducible method for assay of imidazole acetic acid (ImAA) was developed as a modification of that described previously (Watanabe et al., 1983). ImAA conjugate(s) (ImAA‐C), mainly consisting of imidazole acetic acid riboside, could be measured by this method after its hydrolysis to ImAA. The ImAA and ImAA‐C levels in various tissues of rats were measured and the effects of various agents on these levels were studied. The renal clearance values of ImAA‐C in rats and man were similar to the creatinine clearance values, but those of ImAA were 1/40 of those of ImAA‐C, suggesting that the latter is readily excreted in the urine. Consistent with this idea, the urinary excretion of ImAA‐C was found to increase much more than that of other histamine metabolites during late pregnancy, when the foetus produces much histamine. 1984 British Pharmacological Society