Altered Endothelium-Dependent Vasoreactivity of Aortic Rings Follows L-Arginine and Potassium Co-Supplementation in Rats

Purpose: The use of L-arginine and potassium chloride separately as supplements has been reported to result in altered vascular reactivity. The concentration of either agent used has varied widely and there has been no report on the outcome of combined supplementation with both agents on vascular reactivity. We therefore designed this study to measure thoracic aortic ring reactivity after five-week co-supplementation with 1% L-arginine and 0.75% potassium chloride. Methods: Endothelium-intact and endothelium-denuded aortic rings obtained from Sprague- Dawley rats which received the combined supplements were subjected to graded concentrations of carbachol or noradrenaline in organ baths. The maximum responses (Emax) and the negative logarithm of the concentration producing 50% of maximum responses (pD2) were computed as indices of vasoreactivity. Results: Co-supplementation significantly enhanced the relaxant effects of carbachol irrespective of the status of the endothelium although relaxation was by far higher in endothelium-intact rings. In concentration-response curves obtained with noradrenaline, Emax and pD2 values were significantly (P < 0.05) reduced in endothelium-intact rings obtained from rats which received the supplements. In endothelium-denuded rings, responses to noradrenaline were not significantly different from those of control. Conclusion: Co-supplementation with the agents enhances the relaxant effect of carbachol independent of the status of the endothelium while attenuating responses to noradrenaline in endothelium-dependent manner. This suggests that oral L-arginine and potassium cosupplementation may possess beneficial vascular effects.