[ROLE OF THROMBOXANE AND LEUKOTRIENES IN MECHANISMS OF CONTRACTILE REACTIONS OF PORTAL VEIN, INDUCED BY ACETYLCHLINE AND PHENYLEPHRINE].

Effects of picotamide and zileuton on tonic contractile activity of the rat portal vein preparations, induced by acetylcholine (2.10(-5) mol/1) and phenylephrine (5.10(-7) mol/1) were investigated. Conversion of arachidonic acid products (prostaglandins, leukotrienes) synthesized by endothelial cells, plays an important role in the local regulation of vascular tone. The compounds formed in a cascade of enzymatic transformations can modulate the effect of other vasoactive factors. Picotamide (6,5.10(-5) mol/1) - thromboxane receptor and thromboxane -synthase blocker - depress acetylcholine-induction tonic contraction of isolated segments of portal vein with intact endothelium by 29% and norepinephrine-induction reduction of 45% relative to the control values. The obtained results indicate a participation of thromboxane and/or endoperoxide H2 in this reaction. Partial inhibition of the contractions by 5-lipoxygenase blocker zileuton(4,2.10(-5) mol/1) at 23% relative to control values suggests, that products of lipoxigenase pathways of arachidonic acid conversion are involved in mechanisms of specified reactions. These data indicate complex mechanisms of regulation of vascular tone of the portal vein, which play an important role eicosanoids. Further study of these mechanisms is necessary for the formation of basic knowledge, as well as to elucidate the mechanisms of occurrence and development of pathological conditions of vessels and the development of methods of their correction.