RED-CELL TRAPPING IN THE RAT RENAL MICROCIRCULATION INDUCED BY LOW-OSMOLAR CONTRAST-MEDIA AND MANNITOL

RATIONALE AND OBJECTIVES. In acute renal failure after ischemia, intra vascular obstruction by trapped red blood cells in the microvasculatur e of the renal outer medulla is a consistent finding. The influence of intravenously injected contrast media (CM) on such obstruction was in vestigated. METHODS. Anesthetized rats were subjected to 45 minutes of unilateral renal ischemia. Red-cell trapping in ischemically injured kidneys and in the contralateral uninjured kidneys was estimated from the intrarenal distribution of Cr-51-labelled erythrocytes after injec tion of ioxaglate or iopamidol in a dose of 1,600 mg I/kg body weight. As an osmolar control substance, mannitol (950 mOsm/kg) was given to a third group and isotonic Ringer's solution was administered to a fou rth group. RESULTS. In the uninjured kidneys, treatment with ioxaglate or mannitol resulted in no red-cell trapping, while the iopamidol-tre ated group showed red-cell trapping in the inner stripe of the outer m edulla in a dose-dependent manner. In the ischemically injured kidneys , both CM and mannitol enhanced the red-cell trapping in the inner str ipe of the renal medulla. CONCLUSION. The results indicate that intrav enously administered ioxaglate and iopamidol enhance the microvascular obstructions evoked by ischemic injury and that iopamidol may induce local impairment in renal medullary microcirculation in a normal kidne y.