AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 2 318-R324, Copyright © 1990 by American Physiological Society
Effect of water or saline intake on heat-induced limb vasodilation in dehydrated baboons
K. L. Ryan and D. W. Proppe
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
Dehydration markedly attenuates the increase in hindlimb blood flow
elicited by environmental heating (EH) in baboons. This study sought to
determine the importance of gradually produced increases in body fluid
osmolality and decreases in body fluid volume in producing this
attenuation. The hindlimb blood flow increases during EH of seven
unanesthetized chronically instrumented baboons were examined during
euhydration, dehydration (64-68 h of water deprivation), and after ad
libitum oral rehydration with either water or a hyperosmotic saline
solution. EH consisted of acute exposure to ambient temperatures of 38-42
degrees C until internal temperature reached 39.5 degrees C. Dehydration
depressed the maximal external iliac artery blood flow (MIBF) and iliac
vascular conductance (IVC) attained during EH in the euhydrated state by 37
and 43%, respectively. Rehydration with either water or saline solution,
however, restored maximal MIBF and IVC to euhydrated levels. Because plasma
osmolality remained at dehydrated levels after rehydration with saline,
hyperosmolality does not produce the dehydration-induced attenuation in
hindlimb blood flow.
