Biotransfornation of nitric oxide, nitrite and nitrate

Summary

Biotransformation of NO, nitrite and nitrate was investigated in rats and mice in a ¹⁵NO inhalation experiment and intraperitoneal injection experiments of ¹⁵N-nitrite and ¹⁵N-nitrate, and the following results were obtained:

• (1) Rats were forced to inhale ¹⁵NO (145 ppm,123 minutes) or were given an intraperitoneal injection of ¹⁵N-nitrite (2 mg animal⁻¹ as ¹⁵N) or ¹⁵N-nitrate (2mg animal⁻¹ as ¹⁵N), and determination of ¹⁵N recovery in urine was made up to 48 h later. The results were 55, 53 and 78% of the inhaled or injected ¹⁵N, respectively.

• (2) ¹⁵N-nitrate in the urine was converted into a 6-nitro derivative of 3,4-xylenol and its identification and quantitative determination were made by the GGMS method. As to ¹⁵N-urea in the urine, identification and quantitative determination were made by the urease method. ¹⁵N was present in the urine of rats after ¹⁵NO inhalation in the form of N0₃ ⁻ and urea. 75 and 24% respectively. In the urine of rats injected with ¹⁵N-nitrite, about 20% of unidentified ¹⁵N-compounds not discovered in the inhalation experiment was found. The content of ¹⁵N-urea in the urine after injection with ¹⁵N-nitrate was lower than that after injection with ¹⁵N-nitrite.

• (3) When ¹⁵N-nitrite (0.617 mg animal⁻¹ as ¹⁵N) was injected intraperitoneally in mice, 60.7, 7.8 and 0.3% of the injected ¹⁵N were found in the urine, feces and exhaled gas (NO, N0₂ and NH₃ in the gas were caught) up to 48 h after injection respectively, and 1.6% was found in the body 48 h after injection, but the remaining 30% of ¹⁵N could not be recovered.