Nephrotoxic effects of iodinated x-ray contrast media in vitro and in vivo : effects on cultured NRK 52-E cells, development of an animal model of impaired renal function and evaluation of biomarkers of nephrotoxicity

Abstract

Iodinated x-ray contrast media (ICM) are used to improve the visibility of internal structures of the body in an x-ray image due to their ability to attenuate x-rays, providing enhanced contrast between regions of interest and the surrounding tissues. Unfortunately, administration of ICM is associated with adverse side effects, including contrast-induced nephropathy (CIN) which remains one of the most important complications of ICM. The work reported in master’s thesis was aimed at investigating the nephrotoxic effects of ICM in vitro and in vivo. This was done by evaluating the effects of ICM in a rat kidney cell line (NRK 52-E), by developing an animal model of impaired renal function to study in vivo effects of ICM, and evaluating potential biomarkers of renal damage caused by ICM in the developed model. Three methods were selected to evaluate the toxicity of three low-osmolal and one iso-osmolal ICM in the NRK 52-E cells, comprising the trypan blue exclusion assay, the MTT assay, and cell death assessment on formalin fixed cells. Cell morphology was included to supplement the selected tests, and an analytical method, ICP-AES, was used to measure uptake of ICM in the cells. An impaired renal failure model to test ICM in rats was developed by pre-tretment with gentamicin. Creatinine, cystatin C, N-acetyl-â-D-glucosaminidase (NAG), ã-glutamyl transferase (GGT), alpha glutathione-S-transferase (á-GST), total protein, and urine cytology were tested as biomarkers of renal damage caused by ICM in the rat-gentamicin model. The osmolality of the contrast agents appeared to be a major cause for the observed in vitro toxicity. A marked difference in cell death was observed between low-osmolal and iso-osmolal ICM, with iso-osmolal being the least toxic. However, the different chemical structures of low-osmolal ICM may also contribute to the toxicity. In the present work uptake of ICM was most likely due to fluid phase endocytosis, and as a consequence, reduced cell viability. The rat-gentamicin model of impaired renal damage proved to be promising and could be used to compare toxicity of different classes of ICM, and for screening novel candidates. Of the biomarkers evaluated, GGT and total protein proved to be suitable biomarkers of renal damage caused by ICM, whereas NAG, á-GST and urine cytology were regarded as promising biomarkers, but which need further evaluation.