Effects of Intake of Nitrate, Nitrite and Isosorbid Dinitrate (ISDN) on Plasma Nitrate/Nitrite Contents in Rabbits

Abstract

Background: The objective of the present study was to demonstrate the changes in plasma
levels of nitrate and nitrite in rabbits after oral (intragastric) administration of inorganic nitrate
(KNO ), inorganic nitrite (NaNO ) and organic nitrate (isosorbide dinitrate, ISDN). 3 2
Material and Methods: Twenty eight rabbits were divided into four groups (7 in each group) and
various doses of these solutions were given via intragastric route. Group-I (control) was given 6
ml distilled water. Group-II (nitrate) was given 500 mg nitrate, group-III (nitrite) 50 mg nitrite and
group-IV 20 mg ISDN per kg body weight per day. The experiment was conducted for 12 weeks
and blood samples were taken at regular intervals. Plasma nitrate and nitrite levels were
determined as stable metabolites of nitric oxide (NO) formation.
Results: Results indicate 28.2±3.3 µmoles/dL nitrate and 21.24±2.8 µmoles/dL nitrite, a
nitrite/nitrate ratio of 0.75 in all 28 rabbits at zero-day. After 1-day of nitrate intake, an 8.1-fold
increase in nitrate content (from 29.3±3.32 to 238.5±48.9 µmoles/dL, p<0.05) and 2.3-fold
increase in nitrite content (from 20.67±2.88 to 48.75±6.36 µmoles/dL) in group-II animals was
seen. No significant change was observed in their levels in group-III and IV animals during this
period. On 2-day, plasma nitrate content decreased to 165.4±18.3 µmoles/dL and nitrite contents
dropped to normal in group-II animals. After 1-week, nitrate content in group-II also decreased to
normal values. However, nitrite content in group-III animals increased 3-fold (from 18.43±3.06 to
57±4.96 µmoles/dL) during 1-week with no increase in nitrate content. No sudden rise or fall in
contents was observed for 12-weeks in all the groups.
Conclusion: The results demonstrate that the plasma nitrate and nitrite contents are not
changed significantly in all four groups in 12-weeks duration (except the initial rise in week-1) and
animals may possess some adaptive metabolic mechanisms to normalize these levels