ABSTRACT
<p><b>AIM</b>To study effects of proanthocyanidins (PA) on contractile activity of isolated aortic smooth muscle in rats and rabbit platelet aggregation.</p><p><b>METHODS</b>Isolated rat aortic muscle rings were adopted to observe the effects of PA on their contraction induced by noradrenaline (NA) or KCl, and their tensions were recorded by BL-310 experimental system of biological function. Rabbit platelet aggregation induced by arachidonic acid (AA), adenosine diphosphate (ADP), and collagen (Coll) was assayed by turbidimetry.</p><p><b>RESULTS</b>PA could significantly inhibit the contraction induced by NA (10(-6) mol/L), low the concentration-response curves of NA and the maximal response on the endothelium-intact or endothelium-denuded aortic rings. But PA couldn't relax the aortic rings precontracted with KCl and had no influence on rabbit platelet aggregation induced by AA, ADP, and Coll.</p><p><b>CONCLUSION</b>PA can inhibit the contraction induced by NA but not by KCl on isolated rat aortic rings. It also has no influence on rabbit platelet aggregation.</p>