Influence of Different Substances on Urinary Enzyme Excretion

Ever since the development of the first ionic monomeric contrast medium in 1952 [31], tri-iodinated benzoic acid derivatives have been of great importance as diagnostic X-ray contrast media. One has to differentiate between two main classes of these agents, the ionic monomer (e.g. amidotrizoate) and dimer (e.g. ioxaglate) class and non-ionic monomer (e.g. iohexol, iopamidol, iopromide, iosimide and metrizamide) and dimer (e.g. SH H 340 AB: 5,5′-oxayldiimino-bis-[2,4,6,-triiodo-N,N′-bis-(2,3-dihydroxypropyl)-N, N′-dimethyl-isophthala-mide]; 300 mg iodine/ml) class. In pre-clinical studies (with experimental animals) as well as in clinical studies (with humans) the aspect of nephrotoxicity is of special importance because of the almost total renal elimination of these water soluble contrast media [34]. However, in these studies, mostly serum urea nitrogen, serum creatinine, proteinuria and cellular components in urine have been used as parameters for detecting nephrotoxicity, in addition to some cases of histomorphological examination of the kidneys in animal experiments. Since determinations of urinary enzymes have been shown to be sensitive in predicting renal lesions in animals and humans [4, 18–21, 32], many X-ray contrast media have now been studied in animal experiments using rats, rabbits and dogs as the animal subjects and including enzyme determinations. This section deals with the effect of some contrast media on the excretion of various enzymes in urine with regard to their localization in different segments of the nephron and their correlation with other parameters such as serum urea nitrogen and creatinine level as well as histomorphological changes in animal species. Many enzymes from different subcellular locations which have been used to assess the early kidney changes in animal species after contrast media application are presented in Table 1.