Effects of angiotensins and catecholamines on the transmembrane potential and isometric force of rattib isolated atria.
The action of angiotensin II (ATII), 1-des-Asp-ATII (Hepta-2-8), angiotensin I (ATI), 1-Sar,8-Gly-ATII and catecholamines on isometric force and transmembrane potential were studied in rabbit isolated atria, driven electrically. In some experiments two microelectrodes were implated to record simultaneously cjamges of intracellular electrical events in the left and in the right atrium: changes of tension were recorded isometrically. In other experiments changes of transmembrane potential were measured with floating microelectrodes. Norepinephrine and epinephrine increased tension, prolonged the plateau phase of the action potential (A.P.) in both atria, while facilitating conduction. ATII and 1-des-Asp-ATII showed similar effects on tension and greater changes on the electrical events of the left than on the right atrium, while ATI was more effective on the right than on the left atrium. 1-Sar, 8-Gly-ATII had no direct effect but prevented or reduced the action of ATII, 1-des-Asp-ATII and ATI, without influencing norepinephrine and epinephrine. All angiotensions except 1-Sar,8-Gly-ATII slightly prolonged the time of conduction. The results indicate that: a)angiotensins and catecholamines prolong the duration of the action potential and induce minor changes of potential overshoot in atrial fibers; b) ATII and 1-des-Asp-ATII act preferentially on the left and ATI on the right atrium; c) 1-Sar,8Gly-ATII inhibits secifically the effects of ATII and ATI in this preparation.
D000200:Action Potentials / Q000187:drug effects; D000809:Angiotensins / Q000494:pharmacology*; D000818:Animals; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D011817:Rabbits
D000809:Angiotensins; D009638:Norepinephrine; D004837:Epinephrine