Meconium stimulates cyclooxygenase-2 expression in rat lungs.

Since meconium aspiration often induces an inflammatory respiratory disorder, we investigated the effects of intrapulmonary meconium on the expression of cyclooxygenase-1 and 2 in rat lungs. Suspension of human meconium was instilled intratracheally into ventilated lungs of anesthetized rats, while control rats received an equal volume of saline. The meconium lungs were ventilated either with air or 100% oxygen, and control lungs were ventilated with air. After 3 h, the lungs were removed and the amount of cyclooxygenase-1 and 2 mRNA was measured by Northern blot analysis. Cyclooxygenase-1 mRNA was clearly expressed in control rat lungs, while cyclooxygenase-2 expression was minimal. Meconium administration markedly upregulated the expression of cyclooxygenase-2 mRNA, while cyclooxygenase-1 expression remained unchanged. Increased expression of cyclooxygenase-2 was detected in rat lungs ventilated with either air or oxygen. Our data thus indicate that meconium aspiration induces pulmonary expression of cyclooxygenase-2, suggesting an important role for prostaglandins in the meconium aspiration-induced inflammation in neonatal lungs.