Fig. 3.
Effect of the percent α-MHC expression on the maximal rate constant of force redevelopment (ktr) after a rapid slack-restretch maneuver. ktr was measured in four groups of rat myocardium with variable expression of α-MHC: 0% α-MHC, hypothyroid [thyroidectomized with propylthiouracil (PTU) treatment; ○]; 15.4% α-MHC, hypothyroid (thyroidectomized without PTU treatment; ▴); 59% α-MHC, euthyroid (□); 81.4% α-MHC (▪); and 97.8% α-MHC, hyperthyroid (thyroid hormone treatment; •). The groups expressing 15.4% and 81.4% α-MHC were obtained from young (2.5–3 mo old) Spraque-Dawley rats. Data are means ± SE.