[Phylogenetic theory of general pathology. Pericytes, function of the distal arterial bed, metabolic arterial hypertension and hypovolemic shock.].

The in vivo roles of pericyte contractile sphincters, smooth muscle cells, endothelial monolayer, precapillary muscle arterioles, exchange and volume capillaries in the physiological balance between peripheral blood pool and the blood pool volume in the distal arterial bed are not fully understood. However, it is highly probable that: 1. There is no primary arterial hypertension. The compensatory biological reaction of arterial pressure (AP) is always secondary, thus indicating the presence of symptomatic or metabolic arterial hypertension (AH). 2. Elevation of AP in proximal arterial bed is a compensatory response to metabolic disorders and impaired microcirculation and metabolism↔microcirculation biological reaction. The response develops locally in the distal arterial bed (muscle arterioles, functional sphincters, pericytes). 3. Metabolic AH is a pathology of the phylogenetically early distal arterial bed , endothelial monolayer, smooth muscle cell and pericyte function. 4. We believe that formation of acute hypovolemic shock is the condition of sphincter (pericyte) atonia in precapillary muscle arterioles with formation of a nonphysiological blood volume in the distal arterial bed when physiological volume of peripheral blood is insufficient to fill the bed. 5. When local disorder in the biological reaction metabolism↔microcirculation is not compensated by endothelium-dependent vasodilation, an efferent innervation signal from the vasomotor center at the entire organism level is sent to the heart and systemic AP increases first in the proximal then in the distal arterial bed. 6. Systemic AP elevation impairs function of the target organs: kidneys, brain and lungs. Each of these organs regulates hydrodynamics in the local pool of extracellular medium, their dysfunction inducing a compensatory response. 7. Metabolic arterial hypertension results from discoordinated systemic compensation of local disorders in the following biological functions: homeostasis, endoecology, trophology and adaptation. This discoordination occurs at the level of paracrine regulated cell communities of functionally different cells which are structural units of each internal organ.