Uptake of inhaled n-butyl nitrite and in vivo transformation in rats

The uptake of butyl nitrite by rats (500 g, one rat/chamber) was determined over a 5-min exposure period. About 44% of the starting amount (771-3855 ppm) of n-butyl nitrite was consumed in 5 min. Three rats per exposure concentration were individually studied for 0-150 min after exposure. Concentrations of blood methemoglobin and plasma nitrate, nitrite, butyl nitrite, and butyl alcohol were examined. No free nitrite ion or butyl nitrite was detectable in the plasma at any time (6.5-150 min) following the exposure. Concentrations at 6.5 min of butyl alcohol, nitrate ion, and methemoglobin increased with increasing exposure concentrations. Plasma concentrations of butyl alcohol were detectable only briefly at 6.5 and 20 min. Methemoglobin levels decreased linearly at higher concentrations and as an approximate first-order process at lower concentrations (less than 15 g/L of whole blood). By 20 min after the inhalation period, plasma nitrate concentrations had decreased from peak levels to higher than baseline steady-state nitrate concentrations. Nitrosothiols were not detectable in the plasma protein fraction.