title: Effects of thrombin and thrombin receptor activating peptides on rat aortic vascular smooth muscle.
abstract: The role of thrombin receptor activation in isolated rat aortic rings was examined. The human thrombin receptor activating peptides (TRAPs) SFLLRNPNDKYEPF (TRAP1-14), SFLLRNP (TRAP1-7) and rat TRAP1-7 (SFFLRNP) all caused concentration-related (0.1-100 microM) contractions of endothelium-rubbed rat aortic rings. Reversal of the first two amino acids in TRAP1-14 ("reverse TRAP1-14") resulted in total loss of activity. The contractions caused by the TRAPs were reduced substantially in endothelium-intact rings due to endothelium-derived relaxing factor release because the reduced contractions were reversed by N omega-nitro-L-arginine or methylene blue. Contractions were significantly but only slightly enhanced by alpha receptor blockade and were not affected by thromboxane- or endothelin-receptor blockade or by cyclooxygenase inhibition. TRAP1-7 had no effect on contractile responses to norepinephrine, serotonin, angiotensin II or endothelin-1; however, pretreatment with nifedipine or removal of extracellular Ca++ markedly inhibited the contraction. Neither human nor rat alpha-thrombin had any contractile effect on rat aortic rings. In cultured rat aortic smooth muscle cells, alpha-thrombin (EC50 = 1.9 +/- 0.7 nM), TRAP1-14 (EC50 = 30 +/- 4 microM) and TRAP1-7 (EC50 = 20 +/- 9 microM) caused concentration-dependent increases in intracellular calcium [Ca++]i, whereas reverse TRAP1-14 was ineffective. The effect of thrombin on [Ca++]i was abolished by the thrombin inhibitor MD-805, whereas the responses to TRAP were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Bristol-Myers Squibb, Pharmaceutical Research Institute, Princeton, New Jersey.
authors.forename: M J
authors.initials: MJ
authors.lastname: Antonaccio
authors.forename: D
authors.initials: D
authors.lastname: Normandin
authors.forename: R
authors.initials: R
authors.lastname: Serafino
authors.forename: S
authors.initials: S
authors.lastname: Moreland
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004730:Endothelium, Vascular / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D013917:Thrombin / Q000494:pharmacology*
chemical_list: D010446:Peptide Fragments; C072032:thrombin receptor peptide (42-55); D009569:Nitric Oxide; D013917:Thrombin; D002118:Calcium