Effects of sarcomere length and temperature on the rate of ATP utilisation by rabbit psoas muscle fibres

Abstract

1. 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 µm, at 10°C, the rate of ATP utilisation in relaxing conditions was 6 ± 1 µM s _1 (mean ± S.E.M., n = 8 fibres); during isometric contraction it was 310 ± 10 µM s _1 (mean ± S.E.M., n = 11). Assuming a myosin active site concentration of 150 µM, 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 µm. 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 µm, but was less strongly dependent on sarcomere length than was isometric force in the range 1.5-2.5 µm.4. The rate of ATP utilisation in relaxing conditions had a Q 10 of 2.5 in the temperature range 7-25°C, but this increased to 9.7 in the range 25-35°C, suggesting that some active force may have been generated in relaxing solution at temperatures above 25°C.5. The rate of ATP utilisation during isometric contraction had a Q 10 of 3.6 throughout the temperature range 7-25°C; this was similar to the Q 10 for isometric force at low temperature (3.5 at 7-10°C) but much larger than that for isometric force at higher temperature (1.3 at 20-25°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.

The depressive effect of Pi on the force-pCa relationship in skinned single muscle fibers is temperature dependent

“…Sinusoidal analysis performed over a wide range of temperatures has determined that the Q 10 of the forward rate constant of force generation is much greater than that of the backward rate constant (53,59). These findings imply that although the overall speed of myosin ATPase is increased at higher temperatures (28), the cross bridge spends a greater proportion of the cross bridge cycle strongly bound to actin (i.e., an increased duty cycle), thereby increasing P o .…”

Impact of biomineralization processes on the Mg content of foraminiferal shells: A biological perspective

“…It is well known that ATP utilization rate increases with temperature. The Q 10 for ATP hydrolysis in rabbit muscle, for example, is 2.5 in the temperature range 7°-25°C, but increases to 9.7 in the range 25°-35°C, [Hilber et al, 2001]. As mentioned before, ATP represents one of the major buffering molecules that binds free Mg…”

Hibernating Bears Conserve Muscle Strength and Maintain Fatigue Resistance

“…While Q 10 coefficient correction factors for muscle contraction strength become nonlinear at extreme temperatures, we never measured a muscle temperature lower than 29Њ or warmer than 36ЊC in these bears. Therefore, we assumed that within the range of temperatures we measured in these bears, Q 10 correction factors were linear (De Ruiter and De Haan 2000;Hilber et al 2001;Wang and Kawai 2001) Muscle fatigue was measured using a 15-min protocol previously employed on humans (Schulte-Mattler et al 2003). The protocol alternated 1 min of stimulation beginning at 0.5 Hz with 2 min of rest.…”