The cardiac inotropic response to secretin is lower in genetically obese (fa/fa) than in lean (fa/?) Zucker rats.
The efficacy and potency of secretin in rat heart was documented by comparing secretin and D,L-isoproterenol effects on: 1. the inotropic response of papillary muscles electrically stimulated in vitro, and 2. adenylate cyclase activity in a crude membrane preparation from heart ventricle. In male adult lean (FA/?) Zucker rats, the extent of the positive inotropic response and the stimulatory effect on adenylate cyclase were similar in magnitude for secretin and D,L-isoproterenol, the two corresponding EC50 values for inotropic effects being 5- to 10-fold lower than the EC50 values for adenylate cyclase stimulation. In male adult obese (fa/fa) Zucker rats, the stimulatory effects exerted by secretin on the inotropic response and adenylate cyclase activity were reduced by 73% and 70%, respectively, while the extent of similar D,L-isoproterenol responses were reduced, respectively, by 29% and 25% only. With D,L-isoproterenol, the EC50 value for the inotropic effect was 5-fold lower than the EC50 value for adenylate cyclase activation whereas both EC50 values were comparable when secretin was used as a stimulant.
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009765:Obesity / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D010210:Papillary Muscles / Q000187:drug effects / Q000503:physiopathology; D051381:Rats; D011924:Rats, Zucker; D011956:Receptors, Cell Surface / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D011964:Receptors, Gastrointestinal Hormone; D012633:Secretin / Q000494:pharmacology*; D013268:Stimulation, Chemical
D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D011964:Receptors, Gastrointestinal Hormone; C029937:secretin receptor; D012633:Secretin; D000262:Adenylyl Cyclases; D007545:Isoproterenol