title: Relationships between pHi and tension in isolated rat mesenteric resistance arteries.
abstract: Investigations into the relationship between pHi and tension were carried out in rat mesenteric resistance arteries. Acute acidosis, induced by ammonium chloride pre-pulse, led to variable and transient tension development, but simultaneous removal of extracellular sodium led to a sustained rise in tension associated with maintained intracellular acidification. Dependence of tension and pHi recovery from acute acidosis on Na/H exchange and anion exchange pathways was demonstrated using pharmacological inhibitors. Additionally, removal of HCO3 suggested the anion pathway involved was Na-dependent HCO3 transport. Removal of extracellular calcium, or pharmacological inhibition of voltage-dependent calcium channels, prevented the tension development in response to NH4Cl pre-pulse in an Na-free medium, but did not affect pHi. Intracellular acidosis resulting from elevation of the PCO2 resulted in initial vasoconstriction followed by profound vasodilatation of arteries pre-contracted with noradrenaline (NA). The response to alkalosis induced by NH4Cl or by lowering the PCO2 led to initial dilatation followed by potentiation of NA-induced tension.
authors.affiliation: Division of Physiology, United Medical School Smooth Muscle Group, London U.K.
authors.forename: J G
authors.initials: JG
authors.lastname: Matthews
authors.forename: J E
authors.initials: JE
authors.lastname: Graves
authors.forename: L
authors.initials: L
authors.lastname: Poston
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000494:pharmacology; D001639:Bicarbonates / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D002352:Carrier Proteins / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010313:Partial Pressure; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers; D014655:Vascular Resistance; D014661:Vasoconstriction
chemical_list: D000838:Anions; D001639:Bicarbonates; D015220:Calcium Channels; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D002245:Carbon Dioxide; D012964:Sodium; D002118:Calcium; D009638:Norepinephrine