Effect of radiologic contrast material on cell volume regulation in proximal renal tubules from trout (Salmo trutta)

Rationale and Objectives. Most radiographic contrast media (CM) are hyperos motic and pose an osmotic threat to cells they are in contact with. To stud y these effects at the cellular level, cell volume regulatory mechanisms we re observed in proximal renal tubules following exposure to the CM iohexol, ioxaglate, and iodixanol. Materials and Methods. Isolated renal tubules from trout (Salmo trutta) wer e exposed to 5% vol/vol iohexol (326 mOsm), ioxaglate (314 mOsm), or iodixa nol (300 mOsm) or mannitol (to achieve the same osmolalities), and cell vol ume changes were observed videometrically. Results. Iohexol and ioxaglate solutions induced a rapid shrinkage (12%-13% ) not followed by cell volume regulation. Without CM (same osmolality), the cells shrank 11% but then showed a 77%-88% volume recovery. This reswellin g was inhibited by 55% with the Na+, K+, Cl- symporter inhibitor bumetanide (50 mu mol/L). Iodixanol did not significantly affect cell volume. Tubules preincubated with CM or mannitol were then stimulated with a hyposmotic Ri nger solution (160 mOsm) resulting in a 26%-36% cellular volume increase. C ompared with results of experiments without mannitol and CM, preexposure to iohexol or ioxaglate almost completely inhibited the expected regulatory s hrinkage phase, while previous exposure to hyperosmotic solutions with mann itol reduced the shrinkage response by 40%-53%. Conclusion. In this system, the hyperosmotic iohexol and ioxaglate cause ce ll shrinkage followed by an impaired cell volume regulatory response. Expos ure to these two CM also inhibits cell volume regulation on hyposmotic stim ulation. The isosmotic iodixanol has no such effects. These changes appear to some extent to be a result of the CM's degree of hyperosmolality, but th is property alone does not explain these findings.