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Endothelial nitric oxide synthase and caveolin-1 are co-localized in sinusoidal endothelial fenestrae
H Yokomori1, M Oda, M Ogi
1Department of Internal Medicine and Laboratory of Pathology, Kitasato Medical Center Hospital, Saitama and Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan. yokomori-hr@kitasato.or.jp
Background/Aims:
Nitric oxide is synthesized in diverse mammalian tissues by a family of calmodulin-dependent nitric oxide synthases (NOS). Caveolin, the principal structural protein in caveolae, interacts with endothelial NOS leading to enzyme inhibition in a reversible process modulated by Ca++-calmodulin. The aim of the present study was to clarify the ultrastructural localization of eNOS and caveolin-1 in hepatic sinusoidal endothelium by an electron immunogold method.
Methods:
Male Wistar rats were used. Liver tissues and hepatic sinusoidal endothelial cells isolated from rat livers by collagenase infusion were studied. For immunohistochemistry, liver specimens were reacted with anti-eNOS or anti-caveolin-1 antibody. The ultrastructural localization of eNOS or caveolin-1 was identified by electron microscopy using an immunogold post-embedding method.
Results:
Immunohistochemical studies using liver tissues localized endothelial NOS in hepatic sinusoidal lining cells, portal veins and hepatic arteries; and caveolin-1 in sinusoidal lining cells, bile canaliculi, portal vein and hepatic arteries. Immunogold particles indicating the presence of eNOS and caveolin-1 were demonstrated on the plasma membrane of sinusoidal endothelial fenestrae in liver tissue and also in isolated sinusoidal endothelial cells.
Conclusion:
Endothelial NOS and caveolin are co-localized on sinusoidal endothelial fenestrae, suggesting that interaction of the two may modulate cellular regulation of NO synthesis.