0888. Administration of tetrahydrobiopterin (BH4) protects renal microcirculation after ischemia and reperfusion

Methods Nineteen adult sheep were anesthetized, mechanically ventilated and invasively monitored. Renal blood-flow was measured continuously through a left lumbotomy using a peri-vascular flow probe (Transonic, USA) and an aortic clamp was positioned above the renal arteries. After surgical preparation and stabilization, animals were randomized into 3 groups (SHAM=5, I-R=7, I-R+BH4=7). SHAM animals underwent surgical preparation but no aortic clamping was performed. The I-R groups were exposed to 1 hour of aortic ischemia. The I-R+BH4 group received 20 mg/kg of BH4 before aortic clamping. Animals were followed for a maximum of 6 hours after reperfusion. Renal microcirculation was evaluated at baseline, and 1, 4 and 6 hours after reperfusion using Sidestream Dark Field video-microscopy (Microvision Medical, Netherlands). We calculated perfused small vessel density (PVD), proportion of perfused small vessels (PPV) and heterogeneity of PPV (PPV-HI). Data were analyzed using the generalized