Acute toxicity, distribution, and metabolism of 2,4,6‐trinitrophenol (picric acid) in Fischer 344 rats

Abstract

Picric acid (2,4,6-trinitrophenol) is widely used in industry, by the military, and as a research/clinical chemistry reagent. Characterization of the toxicity of this chemical has been limited. Thus the acute toxicity, distribution, and metabolism of picric acid were investigated using Fischer 344 rats. The LD50 for picric acid following oral dosing of male and female rats was established as 290 and 200 mg/kg, respectively. Blood gas analysis indicated severe acidosis during acute intoxication. Metabolism of picric acid was limited to reduction of nitro groups to amines. Metabolites isolated from urine included N-acetylisopicramic acid (14.8%), picramic acid (18.5%), N-acetylpicramic acid (4.7%), and unidentified components (2.4%). Approximately 60% of the parent picric acid was excreted unchanged. The plasma half-life for picric acid was 13.4 h with a gut absorption coefficient (ka) of 0.069 h-1. Twenty-four hours following oral administration of [14C]picric acid (100 mg/kg), the primary depots of radioactivity (per gram tissue basis) were blood, spleen, kidney, liver, lung, and testes. Respective tissue/blood ratios were 0.37, 0.31, 0.28, 0.26, and 0.22. All other tissue assayed had partition ratios < 0.20, with brain and adipose tissue having the least amount of radioactivity. Tissue/blood ratios were essentially maintained over a 48-h postadministration period. Binding (in vitro) of [14C]picric acid to plasma proteins (whole blood preparations) demonstrated both high- and low-affinity binding sites, with dissociation constants of 3.18 x 10(-6) and 2.85 x 10(-4) M, respectively. The findings of this investigation provide information on the acute toxicity, metabolism, and distribution of picric acid, which can be used in risk assessment analyses and in the design of subchronic and chronic toxicity tests.