FIGURE 3.

P_i release rates at successive phases in the contraction protocol. P_i release rate expressed relative to the myosin head concentration (see text). Rates for the successive phases in the protocol shown in Fig. 1 at 32 μmol/liter of Ca²⁺ (gray bars) and 1 μmol/liter of Ca²⁺ (white bars). First turnover, during the time taken for the first 120 μmol/liter of P_i to be released. Isometric phase, at 0.4 s of isometric contraction at SL 1.9 μm. During stretch, average rate during stretch from SL 1.9 to 2.1 μm. After stretch, average rate during isometric phase at SL 2.1 μm. During release, average rate during shortening from SL 2.1 to 1.9 μm. End isometric, average rate during isometric phase at SL 1.9 μm. Error bars indicate mean ± S.E. for 6 trabeculae. *, p < 0.05.