AJP - Heart and Circulatory Physiology, Vol 249, Issue 2 380-H385, Copyright © 1985 by American Physiological Society
Decreased membrane fluidity and beta-adrenergic responsiveness in atherosclerotic quail
K. G. Lurie, J. H. Chin and B. B. Hoffman
The effects of increased cholesterol on erythrocyte membrane fluidity and
beta-adrenergic function were studied in a quail model of atherosclerosis.
Birds fed a cholesterol-supplemented diet developed severe atherosclerosis
and hypercholesterolemia after 6 wk. This cholesterol-enriched diet led to
a markedly elevated serum cholesterol and a 26% increase in the
cholesterol-to-phospholipid ratio in erythrocyte membranes. Electron
paramagnetic resonance spectra measured with 5- and 12-doxyl-stearic acid
spin-label probes were used to estimate the order of quail erythrocyte
membranes. Membrane preparations from cholesterol-fed birds were more
highly ordered near the membrane leaflet surface, as well as deeper in the
membrane interior, compared with controls. beta-Adrenergic receptor
stimulation of adenosine 3',5'-cyclic monophosphate accumulation was
blunted in erythrocytes from the hypercholesterolemic quail. There was no
change in beta-receptor density or affinity in the cholesterol-enriched
membranes. These studies demonstrate that cholesterol incorporation into
erythrocyte membranes in vivo is associated with decreased membrane
fluidity and decreased beta-adrenergic responsiveness. The atherosclerotic
quail may serve as a useful model to further probe the sequelae of
hypercholesterolemia on the function of integral membrane proteins.
