Control of skin blood flow by whole body and local skin cooling in
exercising humans.
P[acute]ergola, Pablo E., John M. Johnson, Dean L. Kellogg, Jr, and
Wojciech A. Kosiba.
Departments of Physiology and Medicine and the Geriatrics Research,
Education and Clinical Center, University of Texas Health Science
Center at San Antonio, San Antonio, TX 78284-7756
APStracts 2:0311H, 1995.
We examined the independent roles of whole body skin temperature (Tsk)
and tissue temperature (local temperature, Tloc) in the control of
skin blood flow (SkBF) during cooling and the roles of the
vasoconstrictor (VC) and active vasodilator (AVD) systems in
mediating these effects. SkBF was monitored by laser-Doppler
flowmetry (LDF) at untreated sites and sites with local VC blockade
by pretreatment with bretylium (BT). Seven subjects underwent 4
sessions of moderate bicycle exercise (20-30 min duration) at neutral
Tsk and Tloc (34 C); neutral Tsk and cool Tloc (27 C); low Tsk (28 C)
and neutral Tloc; and low Tsk and Tloc. Cutaneous vascular
conductance (CVC; LDF/mean arterial pressure) was expressed relative
to the maximum (CVCmax). Cool Tsk increased the threshold level of
internal temperature at which CVC began to rise equally at BT-treated
and at untreated sites (p<0.05). The rate of increase in CVC relative
to internal temperature was reduced by local cooling. Bretylium
pretreatment partially reversed this effect (p<0.05). Thus, a cool
environment results in reflex inhibition of the onset of AVD activity
by cool Tsk and a reduced rate of increase in CVC due, in part, to
norepinephrine release stimulated by cool Tloc.
Received 20 March 1995; accepted in final form 5 July 1995.
APS Manuscript Number H267-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.