Figure 9

Temperature dependence of twitch response. Isometric twitch response (KSE = 10.0) for temperatures ranging from 22°C to 38°C at 5 Hz stimulation. (A) Traces for L-type C a^{2 +} current (I _Ca,L ) showing increasing peak and rate of decline with increase in temperature. The inset shows the temperature dependence of RT_50,I, time required for 50% I _Ca,L inactivation. (B) Traces for [C a^{2 +} ] _myo transient for increasing temperatures show a decline in peak. The inset shows the temperature dependence of RT_50,C, time required for 50% decline in [C a^{2 +} ] _myo from its peak value. (C) Steady state F-Ca relationships for increasing temperature. The inset shows the temperature dependence of half maximal effective concentration (EC₅₀). (D) Traces showing temperature dependence of normalized isometric force developed. The inset shows the relationship between rate of relaxation and rate of contraction. (E) Phase plots of normalized force versus instantaneous [C a^{2 +} ] _myo for increasing temperature overlayed with two steady state F-Ca relationships corresponding to 22°C (+) and 38°C (∗). The inset shows temperature dependence of peak force developed. (F) Sarcomere length corresponding to traces for force developed in panel D.