VASOCONSTRICTION BY ANGIOGRAPHIC CONTRAST-MEDIA IN ISOLATED CANINE ARTERIES

To study the mechanism of the pain produced by contrast media (CM) in peripheral arteriography, we examined the direct effects of low concentrations (1.85-100 mg I/ml) of CM (diatrizoate, iopamidol, ioxaglate, and iotrolan) on helically cut strips of canine blood vessels taken from six different regions. We found that: (a) low concentrations of CM induced vasoconstriction. (b) This occurred immediately after the application of CM and produced sustained constriction. (c) The constriction produced in arteries was dose-dependent. (d) The production and intensity of constriction in the arterial strips differed as follows: cranial mesenteric artery > renal artery > femoral artery > common carotid artery > thoracic aorta > coronary artery. The effects of the CM were, in order of magnitude: diatrizoate > iopamidol > ioxaglate > iotrolan. Differences between CM corresponded with the differences in osmolality of the CM solutions. (e) Low concentrations of meglumine and mannitol also produced vasoconstriction. (f) Constriction caused by all drug samples used was reversible, but the process of relaxation to the original tension was much slower in CM-treated arterial strips than in the other strips. From these results, we confirmed that the incidence and degree of vasoconstriction produced by all drug samples used in this experiment depended on solution osmolality, rather than on chemotoxicity or ionicity. We discuss the physiological mechanism of these results and stress the importance of CM hyperosmolality in vasoconstriction and vascular pain production.