Receptor externalization determines sustained contractile responses to endothelin-1 in the rat aorta.
The role of receptor internalization and recycling in the vasoconstrictor action of endothelin-1 (ET-1) is investigated using a combination of biochemical and physiological experiments. The binding of 125I-ET-1 to cultured aortic myocytes is first defined. Binding is rapidly followed by an internalization of the peptide. Part of the receptor sites then slowly reappears at the cell surface via a cycloheximide-insensitive mechanism. Evidence that externalizing receptors are functional and can trigger contractions is presented. Finally, the actions of cyclo[D-Trp-D-Asp-Pro-D-Val-Leu] (BQ-123), an antagonist of ETA receptors, are investigated. BQ-123 prevents 125I-ET-1 binding to aortic myocytes (dissociation constant, 10 nM). It prevents the constricting action of ET-1 but not that of angiotensin II. BQ-123 also relaxes almost completely aortic strips that have been precontracted by ET-1 irrespective of the time of its addition. It is concluded that a recycling of internalized ET-1 receptors occurs in ET-1-treated aortic myocytes. This process amplifies the action of the peptide and is probably responsible for the unique contractile action of ET-1.
Marsault
R
R
Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice-Sophia-Antipolis, Valbonne, France.
Feolde
E
E
Frelin
C
C
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism* / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D010456:Peptides, Cyclic / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017466:Receptors, Endothelin / Q000378:metabolism* / Q000502:physiology*; D011503:Transglutaminases / Q000037:antagonists & inhibitors
D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D010456:Peptides, Cyclic; D017466:Receptors, Endothelin; D003513:Cycloheximide; D011503:Transglutaminases; C072247:cyclo(Trp-Asp-Pro-Val-Leu)