Cyclosporine and hyperoxia-induced lung damage in neonatal rats.

Cyclosporine effects on hyperoxia-induced histopathological and functional changes in the rat adult lung are controversial and the newborn lung has not been studied. Thus, we evaluated the effects of cyclosporine in young rats after 60% hyperoxia exposure postnatally. Experimental categories included: (1) room air for the first 5 postnatal weeks with daily subcutaneous injections of saline from postnatal day (PN)15 to PN35; (2) room air with daily injections of cyclosporine from PN15 to PN35; (3) 60% oxygen from PN0 to PN14 and then daily saline injections during the following three weeks; (4) 60% oxygen from PN0 to PN14 followed by cyclosporine treatment from PN15 to PN35. Hyperoxia significantly reduced the number of secondary crests and microvessel density, and it increased the mean alveolar size and septa thickness. Cyclosporine treatment did not significantly modify the hyperoxia-induced changes. Conversely, in normoxia, cyclosporine reduced microvessel density and the number of secondary crests. In conclusion, cyclosporine did not modify alveolar and microvascular parameters in hyperoxia exposure, although it caused some changes in normoxia.