title: Contraction of major artery segments of rat by fish neuropeptide urotensin II.
abstract: Urotensin II (U II) caused marked concentration-dependent contractions of helical strips from several major arteries of the rat. The thoracic aorta was most sensitive; the apparent concentration of U II producing half-maximal contraction was 6.8 X 10(-10) M. Papaverine, dibutyryl cyclic AMP, forskolin, and nitroprusside antagonized the contractile responses to U II at the apparent concentrations producing 50% inhibition (IC50) of 7.6 X 10(-6), 2.1 X 10(-4), 2.5 X 10(-6), and 1.5 X 10(-8) M, respectively. Verapamil, a calcium channel-blocking agent, partially inhibited the contractile response to U II at IC50 = 6.5 X 10(-6) M. Maximal relaxation, i.e., a complete inhibition, could not be obtained even at a concentration of 3 X 10(-5) M verapamil. Cyproheptadine reduced the U II-induced contraction at higher concentrations. Phentolamine (10(-5) M), propranolol (10(-5) M), atropine (10(-4) M), tetrodotoxin (10(-6) M), burimamide (10(-5) M), and indomethacin (10(-5) M) did not change the U II-induced contraction. At higher concentration, U II (10(-8) M) induced a small contraction of aortic strips in Ca2+-free Krebs Henseleit solution similar to that of norepinephrine, but the U II-induced contraction was not inhibited by phentolamine or propranolol. The action of U II did not require the presence of endothelial cells. It is concluded that U II acts on vascular smooth muscle and induces the contraction partly through intracellular Ca2+ mobilization but mainly by stimulating the influx of extracellular Ca2+ via potential dependent and potential independent calcium channels.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001158:Arteries / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D004727:Endothelium / Q000166:cytology / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D005399:Fishes / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009479:Neuropeptides / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014579:Urotensins / Q000494:pharmacology*; D014661:Vasoconstriction
chemical_list: D009479:Neuropeptides; D010455:Peptides; D014579:Urotensins; C029677:urotensin II; D002118:Calcium