Ioxitalamate Induces Renal Tubular Apoptosis via Activation of Renal Efferent Nerve–Mediated Adrenergic Signaling, Renin Activity, and Reactive Oxygen Species Production in Rats

To investigate the unrecognized role of renal efferent nerve activity (RENA) in iodinated contrast media (CM)-induced acute kidney injury, we explored the effects of CM on RENA, renal hemodynamics, plasma renin activity (PRA), reactive oxygen species (ROS) production, and renal injury in rats. Four types of CM including ioxitalamate (high osmolar and ionic), ioxaglate (low osmolar and ionic), iohexol (low osmolar and nonionic), and iodixanol (iso-osmolar and nonionic) were given iv (1600 mg I/kg body weight) to urethane-anesthetized female Wistar rats. We measured RENA by electrophysiologic recording techniques, renal blood flow with Doppler ultrasound, PRA by radioimmunoassay, and ROS by an in vivo chemiluminescence method. We graded the severity of CM-induced vacuoles in cortical tubular cells stained by hematoxylin and eosin and apoptosis production in outer medulla by terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay. Besides, the effects of pretreatment with iv beta-adrenoceptor antagonist propranolol (10 mg/kg body weight), antioxidant N-acetylcysteine (100 mg/kg body weight), and renal denervation on CM-induced pathophysiologic parameters were determined. Ioxitalamate significantly increased RENA and renal vascular resistance, PRA, renal ROS production within 1 h, and formation of vacuoles and TUNEL apoptosis in renal tubular cells 2 h later; other CM had less effect on these parameters. On the other hand, propranolol, N-acetylcysteine, or renal denervation partially attenuated the ioxitalamate-aggravated responses on RENA, PRA, ROS production, and vacuole and TUNEL apoptosis formation in renal tubular cells. In conclusion, we suggest that ioxitalamate may induce acute tubular injury via aggravation of RENA, adrenergic signaling, PRA, and ROS production.