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In an attempt to study the role of prostaglandins in the renal vascular response to contrast media in mongrel dogs, renal arterial injections of 6 ml of either the non-ionic contrast medium Iopamidol or the ionic medium diatrizoate meglumine/Na+ were performed, before and after intravenous injection of a buffered solution of acetylsalicylic acid (10 mg/kg) (ASA). Renal blood flow was recorded using non-occluding electromagnetic flow probes. The resting renal blood flow was significantly reduced after ASA. The usual biphasic response to contrast injection was observed both before and after ASA, and using either contrast medium. Analysis of the results failed to show any difference in degree of vasodilation or vasoconstriction after ASA. We conclude that prostaglandins may affect the resting level of renal blood flow but are not mediators of the instantaneous changes in response to contrast injection.

A low osmolality contrast medium (Iopamidol) caused less cardiac disturbance on isolated rabbit heart than a high osmolality medium (Urografin). The same effects were induced by glucose solutions iso-osmolal with the two media. After perfusion with Propranolol (1 microgram/ml) and Cimetidine (1 microgram/ml) the observed effect was unaltered.

Changes in the circulating blood volume following injection of different contrast media and at different sites have been measured in the dog. The results confirm that osmoreceptors in the right atrium play a role for changes in blood volume following injection of a contrast medium. The differential response to individual agents was mainly a function of their osmolality. Atropine appears to moderate the changes.

The synthesis of prostacyclin (PGI2) was studied in isolated perfused rat lungs during the infusion of radiographic contrast media into the pulmonary circulation. At the same molar concentration, diatrizoate, iopamidol, and NaCl fairly equally stimulated the generation of PGI2. A bolus injection of histamine also enhanced the formation of PGI2. A high dose of ionic diatrizoate and hypertonic saline (0.4 mol/l) caused considerable pulmonary edema, which was less marked with non-ionic iopamidol. Experiments with 125I-labeled contrast media indicated rapid efflux of contrast media from the lungs. The present investigation indicates that different contrast media stimulate the synthesis of prostacyclin mainly because of chemical irritation of the pulmonary endothelium. The enhanced formation of endothelium-derived prostacyclin may mediate some systemic and local side effects seen temporarily during intravascular contrast medium examinations.

The new non-ionic contrast agent, iopromide (Schering) is comparable in osmolality and viscosity to the other recently developed low osmolality media, ionic and non-ionic. Its chemotoxicity, as assessed by protein binding, enzyme inhibition and effects on the coagulation cascade is significantly less than that of the conventional media and very similar to that of another established new non-ionic agent, iopamidol (Niopam, Bracco/Merck).