Albumin binding sites are expressed on the abluminal plasma membrane of capillary endothelium.
The presence of albumin binding sites on the abluminal front of vascular endothelium was examined on the capillaries of the adipose tissue. The experimental procedure consisted in injecting interstitially within the rat epididymal fat and epicardial fat, albumin (alone or bearing oleic acid) either conjugated with gold particles (Alb-Au or Alb-OA-Au) or radioiodinated [( 125I]-Alb). In controls, polyethyleneglycol-gold complex (PEG-Au) and [125I]-IgG were used as tracers. The results revealed that: a) albumin binding sites are expressed on the abluminal front of endothelium especially concentrated on plasmalemmal vesicles; b) the retrotranscytosis of albumin conjugates from the interstitium to the capillary lumen is a poorly represented process; c) the binding of the tracers used appears to be time and concentration dependent; d) albumin conjugates do not bind significantly to plasmalemmal vesicles of adipocytes, pericytes and smooth muscle cells; e) PEG-Au and [125I]-IgG do not show a binding pattern similar to that of albumin conjugates.
Raicu
M
M
Institute of Cellular Biology and Pathology, Bucharest, Romania.
Alexandru
D
D
Fixman
A
A
Simionescu
N
N
D000273:Adipose Tissue / Q000098:blood supply / Q000378:metabolism / Q000648:ultrastructure; D000418:Albumins / Q000008:administration & dosage / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure*; D004822:Epididymis; D006046:Gold; D006651:Histocytochemistry / Q000379:methods; D007267:Injections; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D008833:Microcirculation / Q000378:metabolism / Q000648:ultrastructure; D009206:Myocardium; D051381:Rats; D017457:Receptors, Albumin; D011956:Receptors, Cell Surface / Q000378:metabolism* / Q000648:ultrastructure
D000418:Albumins; D007457:Iodine Radioisotopes; D017457:Receptors, Albumin; D011956:Receptors, Cell Surface; D006046:Gold