Characterization of the contractile and relaxant action of the endothelin-1 precursor, big endothelin-1, in the isolated rat basilar artery.
The presence of functional endothelin converting enzyme (ECE) activity in basilar artery ring segments was investigated by measuring the contractile and relaxant effects of big endothelin (ET)-1. Under resting tension conditions cumulative application of big ET1-1 elicited a concentration-related contraction with the concentration-effect curve (CEC) shifted to the right against ET-1 by a factor of 31 and 29 in segments with the endothelium intact or mechanically removed, respectively. Preincubation with the ET(A) receptor antagonist, BQ123, induced an apparently parallel rightwards shift without affecting the maximum contraction. This shift was more pronounced for ET-1 than for big ET-1. With the putative ECE inhibitor phosphoramidon (10(-3) M) in the bath a small rightwards shift of the CEC for big ET-1 was observed in control segments and a more marked one in de-endothelialized segments. In segments precontracted with prostaglandin (PG) F(2alpha) big ET-1 induced a significant although transient relaxation whereas ET-1 did not. However, in the presence of BQ123 both ET-1 and big ET-1 elicited concentration-related relaxation with a significantly higher maximum effect obtained with big ET-1. The potency was 13 fold higher for ET-1, which is markedly less than that found for contraction. The results, therefore, suggest 1) the presence of functional ECE-activity in the rat basilar artery wall, and 2) differences in the functional ECE activity located in the endothelium and media.
Schilling
L
L
Department of Neurosurgery, Division of Neurosurgical Research, University Clinic Mannheim, Faculty of Clinical Medicine Mannheim, University Heidelberg, Theodor Kutzer-Ufer 1-3, D-68135, Mannheim, Germany. lothar.schilling@nch.ma.uni-heidelberg.de
Vatter
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H
Mursch
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Ehrenreich
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Schmiedek
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P
D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D001488:Basilar Artery / Q000187:drug effects* / Q000502:physiology* / Q000648:ultrastructure; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology; D000072396:Endothelin-Converting Enzymes; D016232:Endothelins / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006020:Glycopeptides / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008666:Metalloendopeptidases; D008854:Microscopy, Electron; D010456:Peptides, Cyclic / Q000494:pharmacology; D011498:Protein Precursors / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D016232:Endothelins; D004791:Enzyme Inhibitors; D006020:Glycopeptides; D010456:Peptides, Cyclic; D011498:Protein Precursors; D044022:Receptor, Endothelin A; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D000072396:Endothelin-Converting Enzymes; C072247:cyclo(Trp-Asp-Pro-Val-Leu); C008890:phosphoramidon