The aim of the present study was to observe the expression of sonic hedgehog (Shh) and Ptc signaling molecules in the lungs of newborn rats exposed to prolonged hyperoxia, and to explore the role of the SHH signaling pathway in hyperoxia‑induced lung injury. Newborn Sprague-Dawley rat pups were placed in chambers containing room air or oxygen above 95% for 14 days following birth. The rats were sacrificed after 3, 7 or 14 days and their lungs were removed. Sections were fixed and subjected to hematoxylin and eosin (H&E) staining. Shh and Ptc1 were quantitated by immunohistochemistry. The total RNA and protein were also extracted from lung tissue; real-time PCR (RT-PCR) and western blot analysis were utilized to assess the mRNA and protein expression of Shh and Ptc1. H&E staining demonstrated significant histomorphological changes in the hyperoxia‑exposed lungs at 3, 7 and 14 days of age. The results of the immunohistochemistry, RT-PCR and western blot analysis demonstrated that the expression of Shh was significantly higher in the hyperoxia-exposed lungs at 3, 7 and 14 days, while Ptc1 was significantly elevated at 7 and 14 days. Exposure of the neonatal rat lung to prolonged hyperoxia resulted in acute lung injury and histomorphological changes. Shh and Ptc1 were upregulated in a time-dependent manner in the course of hyperoxia-induced lung injury. The SHH signal pathway may be involved in the pathogenesis of hyperoxia-induced lung injury. This is the first evidence that in vivo hyperoxia induces activation of the SHH signal transduction pathway in newborn lung.

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