The influence of nitric compounds on the reactivity of the isolated bovineabdominal aorta in the presence of lipopolysaccharide (LPS)

Nitric compounds, such as glyceryl trinitrate (GTN) and sodium a,ide, are w ell known vasodilators. Their vasodilative effect is accomplished via nitri c oxide (NO), released during the biotransformation of these compounds in v ascular smooth muscle and endothelium. Lipopolysaccharides (LPS) are endoto xins derived from gram-negative bacteria. In the vascular system, LPS cause severe functional disorders, inducing excessive synthesis and release of N O from the vascular endothelium and smooth muscles. The fact that the effec t of both nitrovasodilatators and LPS on blood vessels is mediated by nitri c oxide prompted us to study their possible synergistic vasodilative intera ction, i.e. we wanted to investigate if there is a functional relationship between the activity of nitric compounds and LPS on the bovine abdominal ao rta. The experiments were conducted on isolated bovine abdominal aorta, incubate d for 4 hours in an organ bath with Tyrode solution. Glyceryl trinitrate an d sodium azide bring about a dose-dependent relaxation of isolated bovine a bdominal aorta previously contracted with noradrenaline. With an EC50 of 1. 531 x 10(-9)M +/- 0.13, glyceryl trinitrate is a more potent relaxant than sodium azide whose EC50 is 2.322 x 10(-9)M+/-0.02. In the presence of LPS, the maximal relaxant effect of GTN was intensified in contrast to the contr ol relaxant effect of GTN on isolated bovine abdominal aorta. The relaxant effect of sodium azide in the presence of LPS was significantly intensified in contrast to the control relaxant effect of this nitric compound. The ap plied lipopolysaccharide definitely induced the production of NO, which, to gether with NO derived from nitric compounds (glyceryl trinitrate and sodiu m azide), caused greater maximal relaxation of the isolated blood vessel, i .e. pretreatment with LPS enhances the biotransformation of both nitric com pounds; to a higher degree of sodium azide.