Efflux of cholesterol and phospholipids derived from the haemoglobin-lipid adduct in human red blood cells into plasma.
OBJECTIVE
The interior of red blood cells (RBCs) contains a variable amount of cholesterol and phospholipids bound to haemoglobin (Hb). This current study was devised to determine if this pool of lipids (termed Hb-Ch) was available for exchange with plasma lipoproteins.


METHODS
We studied the in vitro efflux of lipids from human RBCs into fasting plasma in men with either low (control group) or high Hb-Ch (study group).


RESULTS
When plasma was incubated with a two-fold excess of autologous RBCs the plasma cholesterol level increased due to a decrease in the level of cholesterol from the RBC membrane (in the control group) and due to a decrease in the level of cholesterol both from the RBC membrane and the Hb-Ch fraction (in the study group). The loss of Hb-Ch-derived phospholipids during lipid efflux was roughly equal to that of Hb-Ch-derived cholesterol. The loss of RBC cholesterol into plasma high-density lipoproteins (HDL) was more pronounced in our study group and correlated with the loss of cholesterol from Hb-Ch.


CONCLUSIONS
The Hb-Ch adduct significantly contributes to the lipid efflux from RBCs into plasma. The majority of cholesterol released from Hb-Ch appears in the plasma HDL fraction suggesting that Hb-Ch may play a role in reverse cholesterol transport in vivo.
Nikolić
Milan
M
Faculty of Chemistry, University of Belgrade, Studentski trg 16, P.O. Box 158, 11001 Belgrade, Serbia. mnikolic@chem.bg.ac.yu
Stanić
Dragana
D
Baricević
Ivona
I
Jones
David R
DR
Nedić
Olgica
O
Niketić
Vesna
V
D000328:Adult; D001692:Biological Transport; D002784:Cholesterol / Q000097:blood / Q000378:metabolism*; D008078:Cholesterol, LDL / Q000097:blood / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005215:Fasting / Q000097:blood; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010743:Phospholipids / Q000097:blood / Q000378:metabolism*; D010949:Plasma / Q000378:metabolism*; D011485:Protein Binding; D013997:Time Factors
D008078:Cholesterol, LDL; D006454:Hemoglobins; D010743:Phospholipids; D002784:Cholesterol