IN VIVO FLUORESCENCE MICROSCOPY OF KIDNEY SUBCAPSULAR BLOOD FLOW IN MICE EFFECTS OF CYCLOSPORINE, (NVA)-CYCLOSPORINE, AND ISRADIPINE, A NEW CALCIUM ANTAGONIST

Abstract

The subcapsular kidney microcirculation in mice was observed through a fluorescence microscope, recorded on videotape, and examined for response to infusions of cyclosporine A (CsA) and cyclosporine G (CsG). Coded video recordings were evaluated by a semiquantitative method. CsA infusion (1.6 .+-. 0.4 mg/kg/min) induced a nearly complete inhibition of the subcapsular blood flow. At lower infusion rates (0.46 .+-. 0.2 mg/kg/min), the blood flow inhibition was less pronounced. CsG infusions at corresponding rates induced significantly less inhibition. Pretreatment with a new calcium antagonist, isradipine (18-20 .mu.g/kg bwt), completely prevented the CsA-induced impairment of subcapsular microcirculation. The calcium antagonist, however, did not improve blood flow when administered after induction of inhibition by CsA (16.8 .+-. 2.5 mg/kg), emphasizing the importance of pretreatment. This study suggests hypoperfusion due to vasoconstriction as an important pathophysiologic mechanism for CsA-induced nephrotoxicity. CsG, when given at corresponding rates, induced less inhibition of the blood flow. Pretreatment with a calcium antagonist, isradipine, completely prevented a CsA-induced inhibiton of blood flow, suggesting a potential value in the prevention of CsA-induced nephrotoxicity.