Histopathological Effects of High Nitrate Ingestion on Lungs in Rabbit

Nitrate when ingested are converted to nitrite in the digestive system and absorb in blood causing methemoglobinemia. Some recent studies have indicated the prevalence of a high percentage (40-82 %) of cases of acute respiratory tract infection with history of recurrence in children drinking high nitrate in water than that reported for areas of low nitrate concentration. Therefore an experimental study was conducted in 10 rabbits between three and half month to four month of age having weight ranging 1.310 kg to 10720 kg. Five groups A, B, C, D & E were formed with two rabbits in each group. The control group A was administered water orally having 06 mg/liter. Group B to E (experimental groups ) were administered water orally having concentration of 100mg/liter, 200mg/liter, 400mg/liter & 500mg/liter of nitrate respectively for 120 days. During experimental period the difference in general behavior of rabbits were noted. After that rabbits were anaesthetised & sacrificed according to guidelines of ICMR and lungs were removed & processed for paraffin sections, hemotoxyllin and eosin staining was done for microscopic observations. During experimental period, the animals were lethargy on 75th day and cyanosis appeared on nails, lips, tongue & sclera on 90th day (mainly in rabbits of group D & E). The respiration rate & heart rate were increased with loss of weight. The rabbits of experimental groups passes stool with mucous on 45th day and had diarrhea on 90th day. The microscopic study revealed epithelial hyperplasia and lymphoid aggregation in the respiratory parenchyma. In higher group the lungs were infiltrated with inflammatory cells in inter alveolar space with abundance of Type-2 pneumocytes in the alveolar epithelium.