RENAL TUBULAR EFFECTS OF DIURETICS AND X-RAY CONTRAST-MEDIA - A COMPARATIVE-STUDY OF EQUIMOLAR DOSES IN HEALTHY-VOLUNTEERS

RATIONALE AND OBJECTIVES. The isotonic nonionic contrast medium iodixanol has been shown to increase urinary enzyme excretion less than the hypertonic contrast medium iopentol. The authors investigated whether this could be caused by different molar loads using enzyme excretion after diuretic administration as a model. METHODS. Matching molar doses of mannitol were given to two groups of 10 healthy volunteers. Furosemide was administered perorally to a third group of 10 persons. Urinary enzyme excretion was sequentially measured, and the results were compared to our previous findings after contrast-media administration. RESULTS. Equimolar doses of mannitol and contrast media (CM) induced similar changes in urine volume and free water clearance. Mannitol and furosemide increased the urinary excretion of N-acetyl-beta-glucosaminidase (NAG) and alkaline phosphatase (ALP) in the period 0 to 4 hours after administration, i.e. during peak diuresis, whereas both CM increased ALP significantly more, their effects still evident at 24 to 48 hours. Iodixanol had no effect on urinary NAG excretion, but iopentol increased NAG more than did mannitol. CONCLUSIONS. The early effect of CM on urinary enzyme excretion can be related, in part, to the increased diuresis, but the late effect apparent at 24 to 48 hours cannot be explained by the osmotic load of the CM.