title: Effect of an exercise run to exhaustion on cAMP in the rat heart.
abstract: The purpose of this investigation was to determine whether adenosine 3',5'-cyclic monophosphate (cAMP) content is increased in vivo in the heart as a result of exercise at a time when there is rapid cardiac glycogen utilization. Rats were run to exhaustion on a treadmill for a period of 164.5 +/- 9.5 min. Blood norepinephrine and epinephrine were significantly elevated approximately 2.5-fold above resting levels at the end of the treadmill run. Myocardial glycogen was reduced by 54.7% at exhaustion compared with control values. Myocardial cAMP was significantly elevated 88% above control levels as a result of the run. Associated with the depletion of myocardial glycogen and the elevation of cAMP was an activation of phosphorylase to its a form. These data suggest that myocardial glycogen metabolism during exercise is, in part, mediated by hormonal influences that are associated with increases in cAMP.
mesh_terms: D000818:Animals; D001831:Body Temperature; D001835:Body Weight; D002395:Catecholamines / Q000097:blood; D000242:Cyclic AMP / Q000378:metabolism*; D005221:Fatigue / Q000378:metabolism*; D006003:Glycogen / Q000096:biosynthesis; D006321:Heart / Q000502:physiology; D008297:Male; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D010762:Phosphorylase a / Q000378:metabolism; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002395:Catecholamines; D006003:Glycogen; D000242:Cyclic AMP; D010762:Phosphorylase a