Effect of metoprolol and esmolol on endothelial function

EFFECT OF METOPROLOL AND ESMOLOL ON ENDOTHELIAL FUNCTIONAim: Despite the advancements in treatment of cardiovascular diseases which took place in the recent century, these diseases still remain to be a major cause of mortality. One of the most important advancements is the discovery of beta receptor blockers.Endothelium is the well distinguished, single layer of epithelial tissue lining the vessel lumen. It has been observed to play important role in maintainanceof cardiovascular homeostasis.Beta blockers bearing a high degree of ß1receptor selectivity is being used widespread including the postoperative cardiac surgery patients. Metoprolol and esmolol are examples of such drugs.The aim of this study is the investigation of the effect of these molecules in organ bath on rat aorta which have endothelium and the aorta deficient from endothelium.Material and methods: 32 male Wistar-Albino rats were randomly allocated into 4 groups and aortic rings were prepared. Group 1 (n=8) contains aortic rings with intact endothelium (Metoprolol+endothelium) and group 2 contains (n=8) aortic rings deprived of endothelium (Metoprolol-endothelium) where metoprolol was added into both tissue baths. In the same manner esmolol was added to tissue baths which contain aortic rings with endothelium (Group 3, n=8) (Esmolol+endothelium) or to the baths that contain rings devoid of endothelium (Group 4, n=8) (Esmolol-endothelium). Rats were sacrificed, thoracic aorta were gently removed and sliced into segments of aortic rings each 3-4 mm. in length then preserved in Krebs solution. As to obtain dysfunctional endothelium, endothelium was damaged through application of pressure over luminal side of aortic rings by the use of a metal forceps which will constitute endothelium deprived groups (Groups 3 and 4). Aortic rings were then suspended in tissue baths in Krebs solution (37?C, %95 O2/%5 CO2, pH 7.4) and connected to a transducer system for measurement of isometric tension force. Norepinephrine (1?M) was added to baths and thereafter acethylcholine induced endothelium dependent vasodilator responses were recorded. Those aortic rings which failed to exhibit vasodilation response to acethylcholine were assumed to be endothelium deprived. Following maintenance of standart equilibrium phase dose response to esmolol and metoprolol was studied.Findings: There was no significant difference in vasodilatation response to metoprolol between the groups which have intact or damaged endothelium. Also we did not observe any statistically significant difference in vasodilatation response to esmolol, in the group which has intact endothelium as compared to the group that has damaged endothelium. Esmolol was found to cause distinctly more vasodilatation response than metoprolol when the endothelium denuded groups were compared and the difference reached statistical significance (p<0.05).Conclusion: As a result in this study we observed more vasodilatation response of rat aortic rings in tissue bath when treated with esmolol as compared to metoprolol. The difference in vasodilation response was more evident when the endothelium is denuded.Key Words: Metoprolol, esmolol, endothelial dysfunction, vasodilatation.