Vasoactive peptides and regulation of hemodynamics in different functional states of the organism.
It is important to emphasize that the biochemical systems participating in humoral hemodynamic regulation may function at any level of the circulatory homeostasis: in the blood as a biological fluid constantly circulating along the vessels, at the microcirculatory bed where the exchange with tissues is realized, on the tonic activity of the resistive and capacitance vessels, defining the systemic blood pressure rate and organ redistribution, or, finally, on the main motive force of the blood, the heart. The interrelations of some molecular factors form the biochemical basis for the interaction of the main humoral systems. These factors are kallikrein for kinins and converting enzyme for the renin-angiotensin system, 9-ketoreductase and phospholipase for kinin and prostaglandin systems, and Hageman factors for coagulation, fibrinolysis, and kininogenesis systems. This main scheme includes "functional" connections, which are defined by a physiological interaction, and those between the central and peripheral nervous systems. We may, evidently, postulate an important biological regularity of a multi-functional participation of the same physiologically active factors in maintaining circulatory homeostasis. On the other hand, we have to emphasize the functional unity and joint correlating actions of different biochemical blood systems.