DISTRIBUTION OF CHARGED SITES ON LYMPHATIC ENDOTHELIUM

Abstract

The charge distribution on the luminal and
abluminal aspects of fixed and living lymphatic
endothelium was examined with particular emphasis
on the endocytotic vesicular system and interendothelial
junctions. Native ferritin (NF; pl
= 4.5), when administered abluminally to perfused
lymphatics, entered endocytotic vesicles and
abluminal and luminal caveolae; NF was also
found in intercellular channels. In contrast, NF
when applied luminally was largely excluded
from both luminal caveolae and intercellular
channels. Cationic ferritin (CF; pl = 8.4) bound
to the discontinuous basal lamina and to the
abluminal plasma membrane, clustering
preferentially around the stomata of abluminal
caveolae . CF did not, however, bind to the
plasma membrane of, or enter, either the
vesicular system or intercellular channels, when
administered abluminally. When added to the
perfusion fluid CF bound to the luminal membrane
and to the infundibula of intercellular
channels. Ruthenium red (RR) and alcian blue
(AB), both cationic stains, bound intensely to the
luminal membrane and much less so to the
abluminal surface, thus simulating the binding
pattern of CF. Unlike CF, however, RR and
AB bound to the membranes of abluminal and
luminal caveolae with the same level of staining
as to the plasma membrane to which they were
attached. These results reflect a marked asymmetry
in the membrane charge characteristics of
endothelial cells.