AJP - Heart and Circulatory Physiology, Vol 243, Issue 5 819-H829, Copyright © 1982 by American Physiological Society
beta-Adrenergic dilator effects in consecutive vascular sections of skeletal muscle
J. Lundvall, J. Hillman and D. Gustafsson
Humoral and neurogenic beta-adrenergic dilatation that influenced the
resistance function, the capillary exchange function, and to some extent
the capacitance function was demonstrated in the vascular bed of cat
skeletal muscle. The beta-adrenergic effects were mainly confined to the
microcirculation, causing dilatation of the precapillary sphincters and the
resistance vessels of small calibre. The microcirculatory effects were
pronounced in response to epinephrine, but blood-borne and nerve-released
norepinephrine also evoked marked effects. The beta-adrenergic inhibition
of vascular tone in the microcirculation may serve in the intact organism
to improve tissue nutrition by facilitating capillary diffusion exchange.
It further seems to regulate transcapillary hydrodynamic exchange, partly
by controlling the precapillary sphincters and the capillary hydrostatic
pressure. The blood-borne catecholamines, especially epinephrine, also
markedly affected total regional vascular resistance and thereby blood flow
by dilator interaction with the concomitant alpha-adrenergic
vasoconstrictor response.
