The rate of ATP utilisation by single permeabilised rabbit psoas muscle fibres was 6 microM s-1 in relaxing conditions and 310 microM s-1 during isometric contraction at 10 degrees C.
The study demonstrates that ATP utilisation in rabbit psoas muscle fibres is highly dependent on temperature and sarcomere length during isometric contraction.
The steady state rate of ATP utilisation by single permeabilised fibres from rabbit psoas muscle immersed in silicone oil was measured using a linked enzyme assay that coupled ADP production to the oxidation of NADH.2. At sarcomere length 2.5 microm, at 10 degrees C, the rate of ATP utilisation in relaxing conditions was 6 +/- 1 microM s-1 (mean +/- S.E.M., n = 8 fibres); during isometric contraction it was 310 +/- 10 microM s-1 (mean +/- S.E.M., n = 11). Assuming a myosin active site concentration of 150 microM, these values correspond to rates of ATP utilisation per active site of about 0.04 and 2.1 s-1, respectively. 3. The rate of ATP utilisation in relaxing conditions was independent of sarcomere length in the range 2.5-4.0 microm. The rate of ATP utilisation during isometric contraction had a dependence on resting sarcomere length similar to that of isometric force in the range 2.5-4.0 microm, but was less strongly dependent on sarcomere length than was isometric force in the range 1.5-2.5 microm. 4. The rate of ATP utilisation in relaxing conditions had a Q10 of 2.5 in the temperature range 7-25 degrees C, but this increased to 9.7 in the range 25-35 degrees C, suggesting that some active force may have been generated in relaxing solution at temperatures above 25 degrees C. 5. The rate of ATP utilisation during isometric contraction had a Q10 of 3.6 throughout the temperature range 7-25 degrees C; this was similar to the Q10 for isometric force at low temperature (3.5 at 7-10 degrees C) but much larger than that for isometric force at higher temperature (1.3 at 20-25 degrees C). 6. Application of the NADH-linked assay to single muscle fibres in oil improves the effective sensitivity and time resolution of the method, and allows continuous measurements of the rate of ADP production during active contraction.
Hilber et al. (Thu,) conducted a other in Rabbit psoas muscle fibres (n=11). Sarcomere length and temperature variations was evaluated on Rate of ATP utilisation. The rate of ATP utilisation by single permeabilised rabbit psoas muscle fibres was 6 microM s-1 in relaxing conditions and 310 microM s-1 during isometric contraction at 10 degrees C.