title: Vascular smooth muscle mechanics in isolated perfused segments of carotid arteries.
abstract: BACKGROUND
  We hypothesized that smooth muscle contraction and relaxation responses in a muscle bath (isometric tension) would be different than responses of intact vessels (isotonic tension).
  
  
  METHODS
  Bovine carotid artery contractile responses to the catecholamine, norepinephrine, and smooth muscle relaxant, 3-isobutyl-1-methylxanthine, were examined in strips of vessels in a muscle bath and in intact whole vessels in an isolated perfused whole-vessel perfusion apparatus.
  
  
  RESULTS
  The maximal tension in the muscle bath depended on the length of the strip. The responses of whole vessels to increasing pressure was curvilinear. The maximal decrease in vessel diameter in intact vessels in response to the catecholamine and norepinephrine occurred at low intraluminal pressures. The dose-response curve to norepinephrine was shifted to the left in intact vessels compared with strips of vessels in the muscle bath, which suggests that whole vessels were more sensitive to norepinephrine. The maximal increase in diameter to increasing intraluminal pressure occurred in the presence of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, which suggests that there was significant intrinsic tone in the vascular smooth muscle.
  
  
  CONCLUSIONS
  These results suggest that there are differences in the contractile properties of the vascular smooth muscle that are related to the ex vivo system used to examine smooth muscle responses. Responses obtained in isolated perfused whole vessels may more closely approximate in vivo responses.
authors.affiliation: Department of Surgery, Medical College of Georgia, Augusta 30912, USA.
authors.forename: H
authors.initials: H
authors.lastname: Jerius
authors.forename: C A
authors.initials: CA
authors.lastname: Bagwell
authors.forename: A
authors.initials: A
authors.lastname: Beall
authors.forename: D
authors.initials: D
authors.lastname: Karolyi
authors.forename: C
authors.initials: C
authors.lastname: Brophy
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001696:Biomechanical Phenomena; D002339:Carotid Arteries / Q000502:physiology; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007537:Isometric Contraction; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D000109:Acetylcholine; D015056:1-Methyl-3-isobutylxanthine; D009638:Norepinephrine