Postural vascular response versus sympathetic vasoconstriction in human
skin during orthostasis.
Jepsen, H., and P. Gaehtgens.
Dept. of Physiology, Freie Universit[umlaut]at Berlin, Arnimallee 22, D-14195
Berlin, Germany
APStracts 2:0010H, 1995.
Sympathetic activation and local vascular smooth muscle reactions to vessel
distension contribute to the increase of vascular resistance in the skin
during orthostasis. The relative contribution of these two mechanisms to the
changes of skin blood flow along the body axis upon standing was investigated
in healthy male subjects by Laser-Doppler fluxmetry (LDF). Compared to
recumbency, LDF in the standing subjects was reduced by -19.6+/- 7.2% at the
forehead and by -69.6+/- 9.6% in the leg. In the absence of hydrostatic
pressure changes, the LDF changes upon standing averaged -29+/- 13%,
independent of skin region, reflecting the effect of vasoconstriction due to
sympathetic activation. The postural vascular response, elicited by lowering
the arm or the leg from heart level, was significantly attenuated in
orthostasis compared to recumbency. The vessel reaction to local alteration
of transmural pressure was studied in the skin of the forehead and lower leg
by application of external pressure in supine subjects. No difference in
vessel responsiveness to changes of transmural pressure was found between
these skin sites. The findings suggest that the changes of skin perfusion in
orthostasis result from a non-additive interaction of height-dependent and
-independent mechanisms.
Received 5 August 1994; accepted in final form 17 January 1995.
APS Manuscript Number H700-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.