Biochemical toxicology and disposition of therminol 66 heat transfer fluid after inhalation or after dietary administration to male sprague‐dawley rats

The objectives of this study were to determine the disposition of Therminol 66 in rats and to determine the effects of this heat‐transfer fluid on liver and kidney microsomal drug‐metabolizing enzymes. Therminol 66 was administered to male Sprague‐Dawley rats at various doses as either a single oral administration at 0, 100, or 300 mg/kg, or as a single 6‐h inhalation exposure at 0 or 350 mg/m3. Animals were killed 48 h after gavage or after termination of inhalation exposure. Additional groups of animals were exposed to Therminol 66 via the diet at 0, 100, 500, or 5000 ppm for 14 d, or via repeated inhalation exposure at 0, 25, 250, or 1200 mg/m3 for 6 h/d for 14 d. These exposure scenarios represent approximately equivalent doses of Therminol 66 by the different routes of administration. No change in body weight was observed after acute oral or inhalation exposure, and little change in body weight was observed in animals administered Therminol 66 via the diet except at the highest dose. There was no cha...