title: Acid-base interactions with noradrenaline-induced contractile response of the rabbit isolated aorta.
abstract: The effect of acidosis and alkalosis on vascular smooth muscle contractions evoked by noradrenaline was studied. Helical strips of rabbit aorta were mounted for isometric tension recording. Acidosis (pH 7.24-6.51) was obtained by either increasing the PCO2 (hypercapnic) and/or lowering the HCO3-concentration (hypobicarbonatic). Acidosis shifted the noradrenaline concentration-response curve to the right in a competitive manner. The maximal developed tension was unchanged at pH 7.24-6.90 and decreased by 30% at pH 6.51. Alkalosis (pH 7.61-8.04) did not alter noradrenaline-evoked contractions. The results suggest that hydrogen ions during acidosis (pH less than 7.40) but not during alkalosis (pH greater than 7.40) exert alpha-adrenoceptor blocking properties.
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D002245:Carbon Dioxide / Q000032:analysis; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology / Q000502:physiology*; D010100:Oxygen / Q000032:analysis; D010313:Partial Pressure; D011817:Rabbits; D013718:Tensile Strength
chemical_list: D003470:Culture Media; D002245:Carbon Dioxide; D010100:Oxygen; D009638:Norepinephrine