Reduced responsiveness to noradrenaline in isolated rat atria exposed to hyperosmotic solutions.
1. The effects of hyperosmotic NaCl and sucrose solutions on the responsiveness to noradrenaline (NA) were studied in isolated rat right and left atria. 2. Sucrose caused subsensitivity to NA and isoprenaline in right atria, which was abolished by atropine. 3. NaCl caused subsensitivity only to NA in both atria, which was reversed by imipramine. 4. Both solutions decreased the maximum tension of left atria after maximal NA and Ca2+ concentrations. 5. The results suggest that hyperosmolality reduces the atrial responsiveness to NA by directly depressing contractility and increasing acetylcholine release. However, if the solute is NaCl, the main mechanism seems to be an increase of the catecholamine neuronal uptake.
Bassani
R A
RA
Departamento de Engenharia Biomédica, Faculdade de Engenharia Elétrica, Universidade Estadual de Campinas, SP, Brazil.
Bassani
J W
JW
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002122:Calcium Chloride / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006982:Hypertonic Solutions / Q000494:pharmacology*; D007099:Imipramine / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D009994:Osmolar Concentration; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology
D006982:Hypertonic Solutions; D012965:Sodium Chloride; D013395:Sucrose; D001285:Atropine; D007545:Isoproterenol; D002122:Calcium Chloride; D007099:Imipramine; D002118:Calcium; D009638:Norepinephrine