Effect of nicardipine and verapamil on in vitro albumin transport in rabbit thoracic aorta.

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Abstract
Calcium antagonists have been shown to have an antiatherogenic effect. We investigated the effect of nicardipine and verapamil on the albumin transport across the media of excised rabbit thoracic aorta. The effect of nicardipine was also tested in deendothelialized arteries. The vessels were incubated for 90 minutes in oxygenated Krebs or 80 mM KCl solutions at in vivo length and at a transmural pressure of 70 mm Hg. The transmural concentration profiles of 125I-albumin across the media were measured by a frozen serial sectioning technique. In deendothelialized arteries, K+ decreased the mean medial uptake of labeled albumin, whereas 10(-7) M nicardipine in Krebs increased the uptake and 10(-9) M nicardipine had no effect. In a K+-rich solution, containing 10(-7) or 10(-9) M nicardipine, the medial uptake was lower than, but not significantly different from, that in Krebs. In intact K+-treated vessels, the wall concentrations near the lumen were increased and concentration gradients across the media were observed, possibly due to an increase in endothelial permeability following K+-induced contraction of the endothelial cells. This effect was reversed by the addition of 10(-7) M nicardipine, but not by 10(-7) M verapamil. Nicardipine and verapamil (10(-7) M) in Krebs solution enhanced the albumin uptake by the media of intact arteries. This effect on the permeability of the media may be related to the antiatherogenic effect of calcium antagonists.