Cardiac activity of some peptide hormones in the frog, Rana tigrina.
1. The cardiac responses of isolated frog (Rana tigrina) atria to peptide hormones were studied. 2. Calcitonin gene-related peptide (CGRP), arginine vasotocin (AVT), bovine parathyroid hormone fragment (bPTH-(1-34)) and oxytocin (OXY) produced dose-related positive chronotropic and inotropic responses; atrial natriuretic peptide (ANP) was negative chronotropic and inotropic; cholecystokinin (CCK), vasoactive intestinal peptide (VIP) were without effects. 3. The dose-related responses under bPTH-(1-34) stimulation but not CGRP or AVT were attenuated in the presence of ANP (300 ng/ml, approximately 0.98 x 10(-7) M). As expected ANP decreased the basal AR and AT responses of the isolated atria and the inhibitory effects were dose-dependent. 4. As shown previously, propranolol blocked the atrial tension stimulated by bPTH (1-34) but did not alter the cardiac responses to CGRP and AVT. 5. In the presence of beta-adrenergic blocker (propranolol 10(-7) M) or ANP (10(-7) M), the AR and AT changes under ISO stimulation in the frog were also decreased. 6. These cardiac changes suggest the cardiac inhibitory effects of ANP are related to beta-adrenoceptor activity and ANP might be a beta antagonist.
Department of Biology, Chinese University of Hong Kong.
K W
KW
Chiu
Y C
YC
Lee
D000818:Animals; D016275:Atrial Function / Q000187:drug effects; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D002766:Cholecystokinin / Q000494:pharmacology; D003864:Depression, Chemical; D004347:Drug Interactions; D005260:Female; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D010121:Oxytocin / Q000494:pharmacology; D011898:Ranidae; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D014668:Vasotocin / Q000494:pharmacology
D002316:Cardiotonic Agents; D009419:Nerve Tissue Proteins; D014660:Vasoactive Intestinal Peptide; D010121:Oxytocin; D009320:Atrial Natriuretic Factor; D002766:Cholecystokinin; D015740:Calcitonin Gene-Related Peptide; D014668:Vasotocin