2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
RESULTS AND DISCUSSION
Arteries, arterioles and veins were found to be more distensible in the arm than in the
leg.
Five weeks of bedrest markedly increased distensibility in arteries, arterioles and
veins of the leg.
Five weeks of pressure habituation markedly decreased distensibility, i.e. increased
wall stiffness, in arteries, arterioles and veins of the arm.
Increased intravascular pressure resulted in local release of ET-1. Since this substance
has a well-documented capacity to increase long-term arterial stiffness in in vitro
settings, we suggest that pressure-induced formation/release of ET-1 might contribute
to the increased vascular stiffness observed after the 5-week pressure-habituation
regimen.
DISCUSSION
It thus appears that the wall stiffness of arteries, pre-capillary resistance vessels and
veins adapts to meet the long-term demands imposed by the hydrostatic pressure
acting locally on the vessel walls.
That removal of the hydrostatic pressure gradients that act along the vessels in erect
posture markedly increase pressure distensibility in dependent blood vessels may
contribute to the orthostatic intolerance observed in long-term bedridden patients and
in astronauts/cosmonauts returning from space missions.
That a limited number of exposures to moderately increased arterial pressure increases
the stiffness in arteries and pre-capillary resistance vessels might have implications
for the pathophysiology of essential hypertension.
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