Effect of antianginal agents on arteriolar diameter in normal and cholesterol-fed rabbits

The effect of antianginal agents on the cutaneous arteriolar diameter in normal and cholesterol-fed rabbits was investigated. The change in the potency of trapidil to dilate arterioles in cholesterol-fed rabbits was relatively minor when compared with normal rabbits. On the other hand, the potencies of other agents decreased markedly in cholesterol-fed rabbits as compared with normal rabbits. For example, in arterioles of 45-50 micron in diameter, the effective doses of tapidil and dilazep at which the agents dilated the vessel by 20% (ED20) were 1.0 and 0.07 mg/kg i.v., respectively, in normal rabbits, and 2.3 and 2.0 mg/kg i.v., respectively, in cholesterol-fed rabbits. The other agents, such as dipyridamole, diltiazem and nifedipine, virtually did not show any dilating effects on arterioles of cholesterol-fed rabbits at the doses which were effective in normal rabbits. The maximum changes in systemic blood pressure and carotid blood flow induced by the administration of trapidil, dilazep or dipyridamole did not decrease in cholesterol-fed rabbits as compared with normal rabbits. These results suggest that it is more desirable to evaluate the therapeutic potency of antianginal agents in cholesterol-fed rabbits than in normal rabbits, and that the action of antianginal agents on arterioles is not dependent on its action on systemic hemodynamics.