title: Calcium- and length-dependent force production in rat ventricular muscle.
abstract: 1. Trabeculae from the right ventricles of rat hearts were ;skinned' by immersion for 30 min in a solution containing the non-ionic detergent Brij-58 at a concentration of 1%.2. The average sarcomere length in the central region of the relaxed preparation was estimated by laser diffraction and set at pre-determined values within the range of 1.9-2.4 mum by adjustment of muscle length. Isometric contractions were then induced by raising the Ca(2+) concentration under carefully controlled chemical conditions.3. The dependence of Ca(2+)-activated force production on sarcomere length over the ascending limb of the length-force relation was examined at Ca(2+) concentrations giving partial and full activation of the contractile system of the muscle.4. The dependence of Ca(2+)-activated force on Ca(2+) concentration was compared at sarcomere lengths on the ascending limb and plateau of the length-force relation.5. The results obtained from both kinds of experiment showed that the sensitivity of the contractile system to Ca(2+) increases with sarcomere length over the ascending limb of the length-force relation.6. Possible explanations for this observation have been discussed.
mesh_terms: D000818:Animals; D001699:Biometry; D002118:Calcium / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D009210:Myofibrils / Q000033:anatomy & histology; D051381:Rats; D011919:Rats, Inbred Strains; D013268:Stimulation, Chemical; D013314:Stress, Mechanical
chemical_list: D002118:Calcium