The relation between intravascular radiographic contrast media (RCM) and myointimal hyperplasia after percutaneous transluminal angioplasty is not known. We have investigated the cytotoxic effects of RCM on human vascular smooth muscle cells ( VSMCs) and their effect on the growth of these cells. The cytotoxic effects of RCM were studied using human VSMCs. The cells after being grown to confluency were exposed for 60 min to 250 mgI ml−1 of diatrizoate, ioxaglate, iopromide, iotrolan and

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... d mannitol solutions. The control group was treated with only 15% fetal calf serum (FCS) containing medium. The viability of the cells was examined using the trypan blue exclusion test. The effect of RCM on growth was assessed by exposing the VSMCs after growth arrest, for either 15 or 60 min to 250 mgI ml−1 of diatrozoate, ioxaglate, iopromide, iotrolan and saturated mannitol solution. There was no significant change in the viability of the VSMCs after 60 min exposure to iopromide, iotrolan, saturated mannitol solution, and after 15 min exposure to diatrizoate or ioxaglate. After exposure to diatrizoate or ioxaglate for 60 min, 16.5±2.2% or 9.2±2.6% dead cells were found, respectively ( p<0.05 versus control ). In the growth assay of VSMCs, diatrizoate, ioxaglate and saturated mannitol solutions reduced the growth rate ( p<0.05 versus control ). No significant change was observed with iopromide and iotrolan. In conclusion, ionic RCM have cytotoxic and cytostatic effects on VSMCs while nonionic media have no effects. There is no direct stimulatory effect of contrast media on the growth of VSMCs. The cytotoxic and cytostatic effects of contrast media seems to be both osmolality and chemotoxicity dependent. Low osmolar non-ionic RCM are not likely to contribute to the mechanisms responsible for myointimal hyperplasia after angioplasty.