In vitro and in vivo release of histamine by contrast media in the rat.

Some contrast media are able to release histamine from isolated mast cells of the rat and produce degranulation of these cells. Such properties are fairly correlated with the ability to increase vascular permeability in vivo and to produce a drop in blood pressure. If histamine is similarly being released in humans many untoward effects of these agents referred to clinically might be thus explained.