Increased o- and p-cresol/hippuric acid ratios in the urine of four strains of rat exposed to toluene at thousands-ppm levels.

Rats (Fisher, Wistar, Donryu and Sprague-Dawley strains) were exposed to 5 approximately 3500 ppm toluene for 8 h, and urine samples were analyzed for hippuric acid and cresols. While hippuric acid increased in proportion to the exposure concentration, a sharp increase in o-cresol excretion was observed at high toluene concentrations so that the o-cresol/hippuric acid ratio was elevated after 500 approximately 3500 ppm exposures. Changes in the p-cresol: hippuric acid ratio were less marked. There were strain differences in toluene metabolism. Fisher rats were highest and Sprague-Dawley rats lowest in o-cresol excretion and in the o-cresol: hippuric acid ratio, whereas Wistar rats excreted p-cresol most abundantly.