Abstract:OBJECTIVE: To investigate the effect of inhaled nitric oxide (NO) on surfactant protein A (SP-A) and mannose binding ability (MBA) in neonatal rats with hyperoxia-induced lung injury. METHODS: Sixty-four neonatal rats were randomly exposed to room air (Control group), >95% oxygen for 6 days (Hyperoxia group), 10 ppm NO for 24 hrs (NO group), and >95% oxygen for 6 days along with 10 ppm NO for 24 hrs (Hyperoxia + NO group). After 2 and 6 days of exposure, the lung pathologic changes, gene and protein expressions of SP-A and MBA were measured. RESULTS: The rats from the Hyperoxia group presented with obvious lung injuries. The SP-A expressions of mRNA (0.81 ± 0.04 vs 1.53±0.25) and protein (59.45 ± 18.37 vs 89.77±16.41) in the Hyperoxia group decreased significantly 2 days after exposure but increased significantly 6 days after exposure (SP-A mRNA 0.81±0.02 vs 0.63 ± 0.03; SP-A protein 93.57±13.71 vs 47.73±21.69) compared with those of the Control group (P<0.05). NO treatment alleviated the hyperoxia-induced pathologic injuries 2 days after exposure. The SP-A mRNA expression (0.55±0.91) in the Hyperoxia + NO group was significantly reduced as compared to both the Control and Hyperoxia groups (P<0.05), and the SP-A protein expression (55.12±17.53) in the Hyperoxia + NO group was noticeably lower than that of the Control group ( P<0.01) 2 days after exposure. The SP-A protein expression in the Hyperoxia + NO group (67.33±18.59) was significantly lower than that of the Hyperoxia group 6 days after exposure (P<0.05). Two days after exposure, the NO group had significantly higher MBA than the Control group (0.821 ± 0.133 vs 0.58 ± 0.158); the Hyperoxia + NO group had significantly higher MBA than the Hyperoxia group (0.43 ± 0.175 vs 0.738 ± 0.141) (P<0.05). CONCLUSIONS: Inhaled low dose NO may decrease SP-A protein expression and increase MBA of the lung tissue. This lessens the pathologic lung injury in neonatal rats with hyperoxia.
