Interactions between cardioregulatory agents in the pericardial space: An experimental study.

摘要

The life saving capacity of appropriate medical management in cardiovascular diseases has inspired intensive research into the regulation of cardiac function. While most of the relevant anatomical compartments within this most critical organ have been well characterized, surprisingly little attention has been given to the compartment in which the entirety of the heart is enclosed: the pericardial space and the pericardial fluid (PF). The general consensus on the physiological role of the pericardial fluid assigns it the function of providing continuous lubrication for the epicardium of the beating heart. In addition to those constituents which serve a hydration function, the pericardial fluid also contains a large number of locally produced and active endogenous agents such as endothelin-1 (ET-1), adenine nucleosides, catecholamines, natriuretic peptides, and angiotensin II (AT II).; We aimed to investigate in the comparatively closed system of the intrapericardial space the cardiovascular effects of several vasoactive agents (which are present in the pericardial fluid in higher concentrations than that in the plasma) and the dynamic interactions influencing their production by the myocardium. Our investigations belong to a comprehensive series of explorations into pericardial agents and their effects. In these particular studies, we examined the relationships of the following agents: the classic cardiostimulatory agents the catecholamines (dopamine and norepinephrine), the aggressive vasoconstrictor peptide endothelin-1, its compensatory metabolite adenine nucleosides and the two major representatives of the myocardial tissue hormones, the natriuretic peptides and angiotensin II.; In our results, we found that dopamine and norepinephrine applied intrapericardially exerted characteristic cardiovascular effects and elicited increasing myocardial release of ET-1 and adenosine, which, could be detected as dose-dependent elevations of their concentrations in the pericardial fluid (i) the elevation of intrapericardial level of ET-1 induced myocardial ischemia with concomitant ST segment elevations on ECG - without significant depression of different cardiovascular variables - and had an increasing effect on pericardial atrial natriuretic peptide concentrations, but not on brain natriuretic peptide levels; (ii) beside its weak or moderate cardiovascular effects the intrapericardially applied ATII stimulated the ET-1 and ANP production in the heart, which was detected as increases of big-ET-1 and ANP concentrations. Meanwhile, the plasma levels of these agents did not change in any of the experiments. (Abstract shortened by UMI.)