title: Direct chronotropic and inotropic responses to guanosine and five different guanine nucleotides in isolated perfused dog atria.
abstract: The effects of guanosine and of five guanine nucleotides on sinus rate and contractile force were investigated using the isolated, blood-perfused dog atrium preparation. Guanosine consistently induced a positive chronotropic and inotropic effect which was not suppressed by treatment with a potent beta-adrenoceptor blocking agent, carteolol. GMP, GDP and CTP induced a biphasic chronotropic and inotropic effect. The potencies for inducing the positive effects of GMP, GDP and GTP were almost the same. However, their rank order of potency for inducing negative effects was GTP greater than or equal to GDP greater than GMP. The negative responses to GTP were not inhibited by atropine. Cyclic GMP and dibutyryl cyclic GMP produced only slight negative chronotropic and inotropic effects but not consistently even at larger doses. The positive chronotropic and inotropic responses to norepinephrine were not modified by treatment with dibutyryl cyclic GMP.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002354:Carteolol / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006151:Guanosine / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology
chemical_list: D006150:Guanine Nucleotides; D006151:Guanosine; D003994:Bucladesine; D001285:Atropine; D006160:Guanosine Triphosphate; D002354:Carteolol; D000109:Acetylcholine; D009638:Norepinephrine