Meconium stimulates cyclooxygenase-2 expression in rat lungs

Since meconium aspiration often induces an inflammatory respiratory disorde r, we investigated the effects of intrapulmonary meconium on the expression of cyclooxygenase-1 and 2 in rat lungs. Suspension of human meconium was i nstilled intratracheally into ventilated lungs of anesthetized rats, while control rats received an equal volume of saline. The meconium lungs were ve ntilated either with air or 100% oxygen, and control lungs were ventilated with air. After 3 h, the lungs were removed and the amount of cyclooxygenas e-1 and 2 mRNA was measured by Northern blot analysis. Cyclooxygenase-1 mRN A was clearly expressed in control rat lungs, while cyclooxygenase-2 expres sion was minimal. Meconium administration markedly upregulated the expressi on of cyclooxygenase-2 mRNA, while cyclooxygenase-1 expression remained unc hanged. 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 inflam mation in neonatal lungs.