The effect of captopril on renal blood flow in renal artery stenosis assessed by positron tomography with rubidium-82

The sequence and magnitude of acute changes in renal blood flow following administration of captopril were determined in a canine model of acute unilateral renal artery stenosis using rubidium-82 and positron emission tomography. Data were recorded in each of nine dogs under three conditions: 1) during a baseline control interval, 2) during renal artery stenosis, and 3) during stenosis with intravenous injection of captopril (1.2 mg/kg). Mean arterial blood pressure was 108 ± 12 mm Hg at control, increased significantly to 125 ± 13 mm Hg (p < 0.01) during stenosis, and decreased to 98 ± 13 mm/hg (p < 0.01) after captopril infusion. Mean renal blood flow was calculated using a steady state single compartment model from the images produced by positron emission tomography. The estimated flow to the affected kidney was 3.37 ± 1.48 ml/min/g at control, 0.86 ± 0.62 ml/min/g during stenosis (p < 0.01), and 0.64 ± 0.57 ml/min/g after captopril administration (p = NS compared with precaptopril value). The estimated flow to the contralateral kidney was minimally reduced from a baseline of 3.84 ± 0.95 to 3.24 ± 1.13 ml/min/g (p = NS) during stenosis and increased after captopril infusion (4.08 ± 0.94 ml/min/g; p = 0.01). These data suggest that repetitive imaging with positron emission tomography can be used to delineate acute changes in renal perfusion following captopril administration.