title: Tyrosine phosphorylation following alterations in arteriolar intraluminal pressure and wall tension.
abstract: Arterioles respond to increased transmural pressure with myogenic constriction. The present study investigated the role of tyrosine phosphorylation in myogenic activity. Cannulated segments of a rat cremaster arteriole were fixed under pressure, followed by incubation with fluorescein isothiocyanate (FITC)-conjugated anti-phosphotyrosine. Smooth muscle cell fluorescence intensity was measured with the use of confocal laser-scanning microscopy. Anti-phosphotyrosine fluorescence intensity in muscle cells of arterioles maintained at 100 mmHg was reduced by the tyrosine kinase inhibitor tyrphostin A47 (30 microM) and increased by the tyrosine phosphatase inhibitor pervanadate (100 microM). In time-course experiments, anti-phosphotyrosine fluorescence increased slowly (over 5 min) after an acute increase in intraluminal pressure, and was dissociated from myogenic contraction (within 1 min). In contrast, angiotensin II (0.1 microM) caused rapid constriction and increased tyrosine phosphorylation. Anti-phosphotyrosine fluorescence was also pressure dependent (10-100 mmHg). Abolition of myogenic activity, either through removal of extracellular Ca2+, or exposure to verapamil (5 microM) or forskolin (0.1 microM) caused a further increase in anti-phosphotyrosine fluorescence. We conclude that transmural pressure and/or wall tension in arterioles causes increased tyrosine phosphorylation; however, this is not involved in the acute phase of myogenic constriction but may be involved in later responses, such as sustained myogenic tone or mechanisms possibly related to growth.
authors.affiliation: Microvascular Biology Group, School of Medical Sciences, RMIT University, Bundoora, Victoria 3083, Australia. t.murphy@rmit.edu.au
authors.forename: T V
authors.initials: TV
authors.lastname: Murphy
authors.forename: B E
authors.initials: BE
authors.lastname: Spurrell
authors.forename: M A
authors.initials: MA
authors.lastname: Hill
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000918:Antibody Specificity; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism*; D001794:Blood Pressure; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000032:analysis / Q000378:metabolism; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D014443:Tyrosine / Q000378:metabolism*; D020032:Tyrphostins / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D020032:Tyrphostins; D014665:Vasodilator Agents; C076715:pervanadate; D000804:Angiotensin II; D005576:Colforsin; D019000:Phosphotyrosine; D014638:Vanadates; D014443:Tyrosine; D014700:Verapamil; D002118:Calcium