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(American Journal of Pathology. 2003;162:557-566.)
© 2003 American Society for Investigative Pathology

Regular Articles

Endothelin-1 Suppresses Plasma Membrane Ca++-ATPase, Concomitant with Contraction of Hepatic Sinusoidal Endothelial Fenestrae

Hiroaki Yokomori*, Masaya Oda{dagger}, Mariko Ogi{ddagger}, Kazunori Yoshimura§, Masahiko Nomura§, Kayo Fujimaki§, Yoshitaka Kamegaya{dagger}, Nobuhiro Tsukada and Hiromasa Ishii

From the Department of Internal Medicine* and the Laboratory of Pathology,{ddagger} Kitasato Medical Center Hospital, Saitama; the Department of Physiology,§ Saitama Medical School, Saitama; the Organized Center of Clinical Medicine,{dagger} International University of Health and Welfare, Tokyo; and the Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan

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.






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Copyright © 2003 by the American Society for Investigative Pathology.