title: Ouabain-like compound changes rapidly on physical exercise in humans and dogs: effects of beta-blockade and angiotensin-converting enzyme inhibition.
abstract: Ouabain, an inhibitor of the sodium pump, has been identified as a constituent of bovine adrenal glands. We were interested whether the release of this cardiotonic steroid is stimulated by physical exercise. Hence, athletes and healthy dogs were subjected to ergometry. Ouabain-like compound (OLC) was measured in venous blood by enzyme-linked immunosorbent assay as well as by (86)Rb+ uptake inhibition (as ouabain equivalents). OLC increased in venous blood of athletes after 15 minutes of ergometry from 2.5+/-0.5 to 86.0+/-27.2 nmol/L (n=51; P<0.001), as did the concentration of a circulating inhibitor of the sodium pump from 7.3+/-1.7 to 129.8+/-51 nmol/L (ouabain equivalents, P<0.05). Half-maximal increase in heart rate and systolic blood pressure occurred at 5.1+/-1.2 nmol/L and at 30+/-1 nmol/L OLC, respectively. On rest, OLC decreased in humans and dogs with a half-life of 3 to 5 minutes. In beagles exposed to moderate exercise on a treadmill for 13 minutes, levels of OLC increased 46-fold (from 3.7+/-0.8 to 166.9+/-91.8 nmol/L; n=6; P<0.005). This effect was suppressed when the dogs had been treated for 3 weeks with the beta1-adrenergic receptor blocker atenolol or the angiotensin-converting enzyme inhibitor benazepril. We conclude that OLC changes rapidly during exercise and is under the control of norepinephrine and angiotensin II.
authors.affiliation: Clinic for Small Animal Internal Medicine and Forensic Affairs, Faculty of Veterinary Medicine, Justus-Liebig-University Giessen, Germany.
authors.forename: Natali
authors.initials: N
authors.lastname: Bauer
authors.forename: Jochen
authors.initials: J
authors.lastname: Müller-Ehmsen
authors.forename: Ulrike
authors.initials: U
authors.lastname: Krämer
authors.forename: Njde
authors.initials: N
authors.lastname: Hambarchian
authors.forename: Carsten
authors.initials: C
authors.lastname: Zobel
authors.forename: Robert H G
authors.initials: RH
authors.lastname: Schwinger
authors.forename: Horst
authors.initials: H
authors.lastname: Neu
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kirch
authors.forename: Ernst-Günther
authors.initials: EG
authors.lastname: Grünbaum
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Schoner
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D001552:Benzazepines / Q000494:pharmacology; D002298:Cardenolides / Q000097:blood*; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D010042:Ouabain / Q000097:blood; D012503:Saponins / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors
chemical_list: D000319:Adrenergic beta-Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors; D001552:Benzazepines; D002298:Cardenolides; D012503:Saponins; C034504:digoxin-like factors; D001262:Atenolol; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; C044946:benazepril