The abnormal mechanical strength-interval curve of hypoxic rabbit papillary muscle.
The effect of hypoxic injury on the mechanical strength-interval curve of rabbit myocardium was studied, using an isolated left ventricular thick papillary muscle preparation. Histochemical staining disclosed a central core of injured tissue enveloped by viable muscle which was sustained by aerobic metabolism, being unaffected by iodoacetate. Mechanical strength-interval curves were derived by measurement of developed isometric tension during various pacing protocols. The phasic recovery of contractile tension, described by the strength-internal curve, was markedly prolonged and partly responsible for reduced tension development. Parameters of the strength-interval curve were determined by linear and monoexponential curve-fitting procedures during various experimental interventions. These parameters indicated that the contractility recovery rate was not altered by acidosis or propranolol, but the early phase of the strength-interval curve (at short test intervals) was augmented by propranolol, and the plateau of the full curve was depressed by acidosis. These observations emphasize that the strength-interval curve must be considered in any study of the effect of a drug or other intervention on the contractility of hypoxic myocardium.
Goodyer
A V
AV
Department of Medicine, Yale University School of Medicine, New Haven, CT 06510.
D000818:Animals; D006321:Heart / Q000503:physiopathology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D010210:Papillary Muscles / Q000378:metabolism / Q000503:physiopathology*; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D013696:Temperature
D011433:Propranolol; D010100:Oxygen