Urinary nitrates and nitrites
Urinary nitrates and nitrites were determined using chemiluminescence as described previously [For nitrate determination, 50 μl of urine was injected into the purge vessel containing 8 ml vanadium (III) chloride solution (~ 0.4 g vanadium (III) chloride in 50 ml 1 M hydrochloric acid). The purge vessel was fitted with a water jacket to allow heating of the reagent to 96 °C and cold-water condenser (6 °C), using a circulating bath. Thereafter, the purge vessel was replenished with reagents as described above. The samples were quantified by comparing the area to the area of known standards of sodium nitrate (1–10,000 nmol). Results are expressed as millimoles and micromoles of nitrates and nitrites respectively.