Hepatic sinusoidal endothelial fenestrae express plasma membrane Ca++pump and Ca++Mg++-ATPase.
OBJECTIVE
In general, intracytoplasmic free calcium ions (Ca++) are maintained at a very low concentration in mammalian tissue by extruding Ca++ against a high concentration of extracellular Ca++, mainly through the activity of the plasma membrane Ca++pump-ATPase. The aim of the present study was to demonstrate by electron cytochemical and immunogold methods the ultrastructural localization of two different types of plasma membrane Ca++-ATPase, i.e. Ca++Mg++-ATPase and Ca++pump-ATPase in the hepatic sinusoidal endothelium.


METHODS
Liver tissues and the isolated hepatic sinusoidal endothelial cell (SEC)s were subjected to the following procedures. The ultrastructural localizations of Ca++Mg++-ATPase were examined by an electron cytochemical method. The ultrastructural localization of Ca++pump-ATPase was identified by an electron immunogold method.


RESULTS
The cytochemical reaction of Ca++Mg++-ATPase was found to be localized on the outer sites of the plasma membrane of sinusoidal endothelial fenestrae (SEF). The immunogold particles indicating the presence of Ca++pump-ATPase were identified on the inner sites (cytoplasmic) of the invaginated plasma membrane of SEF CONCLUSIONS: Both Ca++Mg++-ATPase and Ca++pump-ATPase demonstrated on the SEF plasma membrane may be involved in the regulation of intracytoplasmic Ca++ concentration.
Yokomori
H
H
Department of Internal Medicine, Kitasato Medical Center Hospital, Saitama, Japan.
Oda
M
M
Ogi
M
M
Kamegaya
Y
Y
Tsukada
N
N
Nakamura
M
M
Ishii
H
H
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002469:Cell Separation; D002478:Cells, Cultured; D003034:Coated Pits, Cell-Membrane / Q000201:enzymology* / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000201:enzymology / Q000648:ultrastructure; D008099:Liver / Q000098:blood supply / Q000201:enzymology* / Q000648:ultrastructure; D008297:Male; D008833:Microcirculation / Q000201:enzymology* / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D051381:Rats; D017208:Rats, Wistar
D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases