[Basic research in cardiology].
Phosphorylation of phospholamban and troponin I of dog hearts was measured depending on the cardiac cycle. Myocardium biopsies were obtained with the help of an ECG-triggered cryobiopsy device. A standardized back phosphorylation technique was performed with (32P)ATP and an excess of exogenically applied c-AMP dependent protein kinase, which was followed by electrophoretic fractionation. This standardized method enables quantitative measuring especially of the c-AMP-stimulated protein phosphorylation. A dichotomous behaviour in the phosphorylation of troponin I and phospholamban was detected in the cardiac cycle. Like c-AMP and the c-AMP depended protein kinase troponin I reach a maximum phosphorylation in the systole. In contrast to this, phospholamban in vivo shows the highest degree of phosphorylation in the diastole and drops to a significant lower value (by approximately 25%) in the systole. The surprising dichotomy support the assumption that the Ca-detensivation of the contractile proteins by phosphorylation of troponin I was a dynamic counterregulation in the presence of a high Ca-level takes effect before the Ca-accumulation which can be stimulated by phospholamban. The results show that covalent modifications of regulatory proteins come to pass in the ms-range and have to be considered in distinctive conditions of myocardial function.
Lindeke
A
A
Max-Delbrück-Centrum für Molekulare Medizin, Berlin.
Krause
E G
EG
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001706:Biopsy; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004285:Dogs; D004562:Electrocardiography; D004734:Energy Metabolism / Q000502:physiology*; D006352:Heart Ventricles / Q000473:pathology; D006439:Hemodynamics / Q000502:physiology*; D009206:Myocardium / Q000473:pathology*; D010766:Phosphorylation; D014336:Troponin / Q000378:metabolism*; D019210:Troponin I; D000099211:Phospholamban
D000255:Adenosine Triphosphate; D002135:Calcium-Binding Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D014336:Troponin; D019210:Troponin I; D000099211:Phospholamban
Grundlagenforschung in der Kardiologie.