AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 3 485-R492, Copyright © 1986 by American Physiological Society
Sympathetic activity, lipids accumulation, and arterial wall morphology in rabbits at high altitude
K. Fronek and N. Alexander
The purpose of this study was to investigate the effect of increased
sympathetic nervous activity on arterial wall viability as reflected by its
response to elevated plasma lipids. Our previous finding that vascular wall
viability was reduced by low sympathetic nervous activity indicated that
chronically enhanced sympathetic activity should have the opposite effect.
In this study rabbits were divided into two groups, both of which received
1% cholesterol in the diet. One group was born and raised at high altitude
to induce chronic activation of sympathetic activity, and the other was
raised at sea level. Aorta of high-altitude rabbits exhibited significantly
less lipid accumulation than aortas of sea-level rabbits. This difference
in lipid accumulation was accompanied by elevated norepinephrine turnover
and decreased sensitivity to exogenous norepinephrine of high-altitude
rabbit arteries. Vascular smooth muscle cells of high-altitude rabbits
demonstrated striated increased relative volume density of mitochondria and
decreased nucleocytoplasmic ratio, reflecting lower mitotic rate. These
results are suggestive that enhanced chronic activity of vascular
sympathetic innervation protects smooth muscle from lipid accumulation and
exerts a positive effect on vascular viability.
