L-carnitine and propionyl-L-camitine improve endothelial dysfunction in spontaneously hypertensive rats: Different participation of NO and COX-products

L-carnitine and propionyl-L-carnitine are supplements to therapy in cardiovascular pathologies. Their effect on endothelial dysfunction in hypertension was studied after treatment with either 200 mg/kg of L-carnitine or propionyl-L-carnitine during 8 weeks of spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WXY). Endothelial function was assessed in aortic rings by carbachol-induced relaxation (CCh 10(-8) to 10(-4) M) and factors involved were characterized in the presence of the inhibitors: L-NAME, indomethacin, the TXA(2)/ PGH(2) Tp receptor antagonist ICI-192,605 and the thromboxane synthetase inhibitor-Tp receptor antagonist, Ro-68,070. The effect on phenylephrine-induced contractions was also observed. To identify the nature of vasoactive COX-derived products, enzyme-immunoassay of incubation media was assessed. Involvement of reactive oxygen species was evaluated by incubating with superoxide dismutase and catalase. Nitric oxide production was evaluated by serum concentration of NO2+NO3. Treatment with both compounds improved endothelial function of rings from SHR without blood pressure change. Propionyl-L-carnitine increased NO participation in WKY and SHR. L-carnitine reduced endothelium-dependent responses to CCh in WKY due to an increase of TXA(2) production. In both SHR and WKY, L-carnitine enhanced concentration of PGI(2) and increased participation of NO. Results in the presence of SOD plus catalase show that it might be related to antioxidant properties of L-carnitine and propionyl-L-carnitine. Comparison between the effect of both compounds shows that both may reduce reactive oxygen species and increase NO participation in endothelium-dependent relaxations in SHR. However, only L-carnitine was able to increase the release of the vasodilator PGI(2) and even enhanced TXA(2) production in normotensive rats. (c) 2005 Elsevier Inc. All rights reserved.