Structural adaptation of microvascular networks: functional roles of adaptive responses

• Published in: American journal of physiology. Heart and circulatory physiology 2001-09, Vol.281 (3), p.H1015-H1025
• Main Authors: Pries, A. R, Reglin, B, Secomb, T. W
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - physiology; Animals; Blood Flow Velocity - physiology; Blood Pressure - physiology; Blood Viscosity - physiology; Computer Simulation; Hemodynamics - physiology; Male; Mesentery - blood supply; Microcirculation - physiology; Models, Cardiovascular; Oxygen - metabolism; Rats; Rats, Wistar; Regional Blood Flow - physiology; Signal Transduction - physiology; Space life sciences; Stress, Mechanical; Vascular Patency - physiology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.281.3.h1015

1  Department of Physiology, Freie Universität Berlin, D-14195 Berlin; 2  Deutsches Herzzentrum Berlin, D-13353 Berlin, Germany; and 3  Department of Physiology, University of Arizona, Tucson, Arizona 85724 Terminal vascular beds continually adapt to changing demands. A theoretical model is used to simulate structural diameter changes in response to hemodynamic and metabolic stimuli in microvascular networks. Increased wall shear stress and decreased intravascular pressure are assumed to stimulate diameter increase. Intravascular partial pressure of oxygen (P O 2 ) is estimated for each segment. Decreasing P O 2 is assumed to generate a metabolic stimulus for diameter increase, which acts locally, upstream via conduction along vessel walls, and downstream via metabolite convection. By adjusting the sensitivities to these stimuli, good agreement is achieved between predicted network characteristics and experimental data from microvascular networks in rat mesentery. Reduced pressure sensitivity leads to increased capillary pressure with reduced viscous energy dissipation and little change in tissue oxygenation. Dissipation decreases strongly with decreased metabolic response. Below a threshold level of metabolic response flow shifts to shorter pathways through the network, and oxygen supply efficiency decreases sharply. In summary, the distribution of vessel diameters generated by the simulated adaptive process allows the network to meet the functional demands of tissue while avoiding excessive viscous energy dissipation. shear stress; pressure; conducted response; oxygen transport; mathematical modeling