Histopathological studies on the effects of peroxynitrite on the lungs and trachea of rabbits.

Peroxynitrite (ONOO-) is the reaction product between nitric oxide and the superoxide anion. It is a biological oxidant and cytotoxic anion, produced in vivo, which might cause inflammation and damage to the lungs. This study was designed to investigate whether direct contact with peroxynitrite could cause pathological changes in the airways. Twenty New Zealand rabbits were divided into four experimental groups. They were anesthetised by intravascular injection of thiopental sodium, and peroxynitrite (0.5 mL of a 10 mM solution) was inoculated intratracheally. At 2 h, 24 h, 48 h, and 72 h postinoculation trachea and lungs were isolated for histopathology. The histopathological observations in the lungs were congestion, serous exudation, infiltration of leukocytes and degeneration, which were found to be time-dependent. Changes were similar at 48 and 72 h. Degenerative changes were not progressive. The changes in the trachea were congestion, oedema, leukocyte infiltration, and degeneration of tracheal epithelium. This study shows that peroxynitrite formation in the respiratory tract induces lung inflammation and degenerative changes.