Effect of temperature and calcium on the diastolic length-tension relationship of rat heart muscle.
Experiments were performed on strips from the right ventricle of the rat in order to investigate the influence of temperature and Ca++-removal on the length-tension relationship. Temperature change (22-38 degrees) had no effect on the resting, non-stimulated muscle. The isometric minima curves of the electrically stimulated preparations at 18 degrees and 38 degrees (diastolic length-tension relationship), however, were shifted to the right compared to those at 28 degrees. When temperature decreased (at fixed muscle length), the diastolic tension surmounted a maximum at the optimal temperature (28 degrees) and declined with further cooling. Moreover the electrolyte exchange characteristics (Ca, K, Na), which follow upon a variation in temperature, were studied. The calcium content of the stimulated preparations showed a similar dependence on temperature as the diastolic tension, indicating that calcium might play a role with respect to the influence of temperature on the diastolic length-tension relationship. Indeed an addition of EDTA to the bath solution caused a parallel shift of the isometric minima curve to the right. These results show that an active mechanism might contribute to the increase of diastolic tension in response to stretch.
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D003080:Cold Temperature; D003971:Diastole / Q000187:drug effects; D004492:Edetic Acid / Q000494:pharmacology; D004573:Electrolytes / Q000032:analysis; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000032:analysis; D051381:Rats; D013696:Temperature
D004573:Electrolytes; D004492:Edetic Acid; D002118:Calcium