Endothelin-1 suppresses plasma membrane Ca++-ATPase, concomitant with contraction of hepatic sinusoidal endothelial fenestrae.
Intracytoplasmic free calcium ions (Ca++) are maintained at a very low concentration in mammalian tissue by extruding Ca++ from the cytoplasm against a steep extracellular Ca++ concentration gradient, mainly through the activity of plasma membrane Ca++ pump-ATPase. The present study aimed to elucidate how endothelin-1 (ET-1) affects the morphology of sinusoidal endothelial fenestrae and ultrastructural distribution of plasma membrane ATPases and intracytoplasmic free Ca++ in isolated rat hepatic sinusoidal endothelial cells. Sinusoidal endothelial fenestrae were observed by scanning electron microscope. Ando's electron cytochemical method was used for ultrastructural localization of Ca++-Mg++-ATPase activity, electron immunogold postembedding method for Ca++ pump-ATPase immunoactivity, and antimonate method for intracytoplasmic free Ca++. Addition of ET-1 to sinusoidal endothelial cells significantly decreased Ca++-Mg++-ATPase activity and Ca++ pump-ATPase expression and increased intracytoplasmic free Ca++ concentration, concomitant with a decrease in diameter of sinusoidal endothelial fenestrae. Co-treatment with Bosentan abolished the actions of ET-1. These results suggest that ET-1 suppresses Ca++-Mg++-ATPase activity and Ca++ pump-ATPase expression on the plasma membrane of sinusoidal endothelial fenestrae, thereby attenuating the extrusion of intracytoplasmic free Ca++ into the extracellular space, leading to an increased concentration of intracytoplasmic free calcium ions and contraction of sinusoidal endothelial fenestrae.
Yokomori
Hiroaki
H
Department of Internal Medicine and the Laboratory of Pathology, Kitasato Medical Center Hospital, Saitama. yokomori-hr@kitasato.or.jp
Oda
Masaya
M
Ogi
Mariko
M
Yoshimura
Kazunori
K
Nomura
Masahiko
M
Fujimaki
Kayo
K
Kamegaya
Yoshitaka
Y
Tsukada
Nobuhiro
N
Ishii
Hiromasa
H
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000648:ultrastructure; D002462:Cell Membrane / Q000201:enzymology*; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology*; D004727:Endothelium / Q000502:physiology*; D008099:Liver / Q000166:cytology* / Q000201:enzymology / Q000648:ultrastructure; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D019332:Endothelin-1; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases