[Effect of endogenous metabolites on autoregulation and dilational reserve of coronary vessels]

The experiments have been performed on isolated Langendorff rat's hearts. Perfusion pressure (PP) has been increased from 40 to 120 mm Hg by steps. It has been found out, that captopril, indomethacin and verapamil (blockers of the angiotensin-converting enzyme, eicosanoids synthesis and calcium channels, respectively) increased volume velocity of coronary flow (VVCF) at PP within the range of 80-120 mm Hg, decreased the value of the autoregulation index and the coronary vasodilatory reserve by 28-39%, apparently due to decrease of the basal tone of coronary vessels, while the maximum reactive hyperemia coronary flow was not changed thereby. The blockade of No-synthase by NG-monomethyl-l-arginine (NG-MMLA) caused reduction of VVCF at PP 40 mm Hg by 28.5%, the autoregulation index by 79% and the coronary reserve by 29% due to reduction of reactive hyperemic flow. Captopril and NG-MMLA did not change while verapamil and indomethacin decreased intraventricular pressure. Thus, the decrease of the VVCF, caused by NG-MMLA and its increase caused by addition of inhibitors could be connected with inhibition of the synthesis of substances modulating autoregulation of coronary blood flow, and obviously did not depend on changes in functional activity of myocardium.