Regulation of systolic force and control of free energy of ATP-hydrolysis in hypoxic hearts.
In isolated isometrically working rat hearts during graded, constant pressure hypoxic saline perfusion (PO2 140-700 mmHg) heart rate was changed experimentally between 80 and 400/min. The following parameters were recorded or estimated: peak systolic pressure, dP/dtmax, dP/tmin, oxygen consumption (VO2), venous PO2, ATP, ADP, phosphocreatine, creatine and inorganic P. Free energy of ATP hydrolysis (dG/d xi) was calculated from cytosolic concentration using CK-equilibrium equation. Two predominant responses of the hearts to hypoxia were observed, pronounced negative force frequency relationship; maintained energetic state (Free energy, dG/d xi) at the respective level of hypoxia if contractile force and beating rate were varied by a factor of 4-5. The enhanced force frequency relationship with a maintained free energy level is interpreted in terms of downregulation of EC-coupling (including duration of action potential) which comprises a possible cardioprotective effect.
Kammermeier
H
H
Department of Physiologie, Medical Faculty RWTH Aachen, FRG.
Roeb
E
E
Jüngling
E
E
Meyer
B
B
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006321:Heart / Q000502:physiology; D006868:Hydrolysis; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013599:Systole / Q000502:physiology*
D000255:Adenosine Triphosphate