IOBITRIDOL, A NEW NONIONIC LOW-OSMOLALITY CONTRAST AGENT, AND IOHEXOL - IMPACT ON RENAL HISTOLOGY IN THE RAT

RATIONALE AND OBJECTIVES. To compare the histologic effects on rat tubular cells of two nonionic contrast media with equivalent osmolalities and viscosities. METHODS. Histologic, functional (creatinine clearance), and biochemical (proteinuria and enzymuria) profiles of iohexol and iobitridol (both at 350 mg I/mL) were compared in the uninephrectomized rat. A control group (n = 14) received compared isotonic saline solution, Test substances (3 mL) were injected into the kidney at a rate of 1 mL/minute while transitory ischemia was induced by clamping the aorta above the renal artery. RESULTS. In terms of their (moderate) effects on creatinine clearance, proteinuria, and urinary N-acetyl-beta-D-glucosaminidase activity, no statistically significant difference was detected between the two low-osmolar contrast agents either 24 or 48 hours after injection, However, blinded histologic analysis of the kidneys showed significantly greater epithelial cell vacuolization in the proximal convoluted tubules of the outer cortex with iohexol (14 of 14 rats versus 3 of 14 rats for iobitridol; P <.001). The same degree of vacuolization in the inner cortex was observed for all three substances, Iobitridol also induced fewer congestive lesions in the glomerular capillaries than iohexol (4 of 14 versus 10 of 14, respectively; P <.05) and saline (5 of 6; P <.05). It is difficult to explain the lesser degree of cytoplasmic vacuolization using standard physicochemical parameters. CONCLUSION. Although iobitridol and iohexol showed similar functional and biochemical profiles when selectively injected into the single remaining kidney of rats, iobitridol induced significantly less tubular vacuolization and capillary congestion than iohexol.