The fate of inhaled octane and the nephrotoxicant, isooctane, in rats

Abstract

To determine if inhaled nephrotoxic branched and nonnephrotoxic straight chain alkanes differ substantially in their biological fate, male F344 rats were exposed to 14C-labeled isooctane and octane vapors at ∼ 1 and 350 ppm by the nose-only mode for 2 hr. Radioactivity in exhalant, urine, and feces was determined for 70 hr post exposure, after which residual radioactivity in the rat carcasses was determined. Absorbed [ 14C]-isooctane equivalents were eliminated almost exclusively via the kidneys, while absorbed [ 14C]-octane equivalents were excreted about equally via the kidneys and as 14CO 2. Kidney excretion of isooctane-introduced 14C was protracted over the entire 70 hr postexposure observation period whereas for octane-introduced 14C, kidney excretion was essentially complete after 10–20 hr. About 5% of the [ 14C]octane equivalents inhaled at 1 ppm remained in the carcass 70 hr after inhalation exposure. Two percent of the [ 14C]octane equivalents inhaled at 350 ppm and 1–2% of the [ 14C]isooctane equivalents inhaled at either 1 or 350 ppm remained in the carcass 70 hr after inhalation exposure. The different patterns of excretion of metabolites of isooctane compared to octane may be a factor affecting the differences in nephrotoxicity between these two compounds.