Nitrite and nitrate pharmacokinetics in the dog, sheep, and pony

Elimination kinetics of nitrite and nitrate in the dog, sheep, and pony were determined. The elimination half-lives of nitrite were 0.499, 0.475, and 0.566 hours in the dog, sheep, and pony, respectively; those of nitrate were 44.681, 4.233, and 4.821 hours. Apparent specific volumes of distribution (V'd) of nitrite were variable among the 3 species--1,623.7 ml/kg in the dog, 278.0 ml/kg in the sheep, and 191.6 ml/kg in the pony. The V'd of nitrate were less varied--dog, 238.5 ml/kg; sheep, 291.1 ml/kg; and pony, 209.3 ml/kg. In the in vitro studies on protein binding in canine plasma, the extent of nitrite-protein binding varied directly with concentrations of 5 to 25 mug of NO2 minus/ml (4.5 to 13.6% bound), but inversely with concentrations of 50 to 100 mug of NO2 minus/ml (9.8 to 8.8% bound). Less than 1% of nitrate was bound to canine plasma at equimolar concentrations (5 to 100 mug of NO3 minus/ml).