Deoxygenation-induced alterations in sickle cell membrane
cholesterol exchange.
Kavecansky, Juraj, Friedhelm Schroeder, and Clinton H. Joiner.
Departments of Pediatrics, and Molecular and Cellular Physiology,
College of Medicine University of Cincinnati, and the Cincinnati
Comprehensive Sickle Cell Center, Children's Hospital Medical Center,
Cincinnati, OH 45267-00541 and the Department of Physiology and
Pharmacology, Texas A&M University TVMC, College Station, TX
77843-4466
APStracts 2:0181C, 1995.
Changes in a membrane sterol exchange of sickle red blood cells (SS
RBC) induced by deoxygenation were studied using the fluorescent
cholesterol analogue, dehydroergosterol (DHE). DHE uptake by SS RBC
membrane was measured by the incubation of SS RBC with small
unilamellar vesicles (SUV) containing DHE. Deoxygenation of SS RBC,
but not normal RBC, increased the rate of DHE uptake. DHE membrane
content after 5 hour incubation with SUV in the cell:SUV ratio of 1:1
(mol lipid) was 16.25 +/- 0.94 and 12.22 +/- 0.85 % of total sterol
for deoxygenated and oxygenated cells, respectively. Membrane
spicules isolated from these deoxygenated SS RBC had 3-fold higher
DHE content, suggesting that the increased sterol exchange was
localized to spicules. When isolated spicules were incubated with
DHE-SUV directly, 91 +/- 3 % of membrane sterol was rapidly
exchanged, in contrast to intact RBC in which a maximum of 33% of
sterol could be exchanged. The results suggest that spicule formation
in SS RBC alters membrane cholesterol structure such that a domain of
cholesterol which is normally non-exchangeable becomes readily
exchangeable with exogenous sterol.
Received 9 February 1995; accepted in final form 26 April 1995.
APS Manuscript Number C71-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.