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An analysis of the temperature dependence of force, during steady shortening at different velocities, in (mammalian) fast muscle fibres.

Roots H, Ranatunga KW - J. Muscle Res. Cell. Motil. (2008)

Bottom Line: In shortening, these were increased with increase of velocity so that at a shortening velocity (approximately 4 L(0)/s) producing maximal power at 35 degrees C, T(0.5) was approximately 28 degrees C, DeltaH was approximately 200 kJ mol(-1) and DeltaS approximately 700 J mol(-1) K(-1); the same trends were seen in the tension data from isotonic release experiments on intact muscle and in ramp shortening experiments on maximally Ca-activated skinned fibres.In general, our findings show that the sigmoidal relation between force and temperature can be extended from isometric to shortening muscle; the implications of the findings are discussed in relation to the crossbridge cycle.The data indicate that the endothermic, entropy driven process that underlies crossbridge force generation in isometric muscle (Zhao and Kawai 1994; Davis, 1998) is even more pronounced in shortening muscle, i.e. when doing external work.

View Article: PubMed Central - PubMed

Affiliation: Muscle Contraction Group, Department of Physiology & Pharmacology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.

ABSTRACT
We examined, over a wide range of temperatures (10-35 degrees C), the isometric tension and tension during ramp shortening at different velocities (0.2-4 L(0)/s) in tetanized intact fibre bundles from a rat fast (flexor hallucis brevis) muscle; fibre length (L(0)) was 2.2 mm and sarcomere length approximately 2.5 microm. During a ramp shortening, the tension change showed an initial inflection of small amplitude (P(1)), followed by a larger exponential decline towards an approximate steady level; the tension continued to decline slowly afterwards and the approximate steady tension at a given velocity was estimated as the tension (P(2)) at the point of intersection between two linear slopes, as previously described (Roots et al. 2007). At a given temperature, the tension P(2) declined to a lower level and at a faster rate (from an exponential curve fit) as the shortening velocity was increased; the temperature sensitivity of the rate of tension decline during ramp shortening at different velocities was low (Q(10) 0.9-1.5). The isometric tension and the P(2) tension at a given shortening velocity increased with warming so that the relation between tension and (reciprocal) temperature was sigmoidal in both. In isometric muscle, the temperature T(0.5) for half-maximal tension was approximately 10 degrees C, activation enthalpy change (DeltaH) was approximately 100 kJ mol(-1) and entropy change (DeltaS) approximately 350 J mol(-1) K(-1). In shortening, these were increased with increase of velocity so that at a shortening velocity (approximately 4 L(0)/s) producing maximal power at 35 degrees C, T(0.5) was approximately 28 degrees C, DeltaH was approximately 200 kJ mol(-1) and DeltaS approximately 700 J mol(-1) K(-1); the same trends were seen in the tension data from isotonic release experiments on intact muscle and in ramp shortening experiments on maximally Ca-activated skinned fibres. In general, our findings show that the sigmoidal relation between force and temperature can be extended from isometric to shortening muscle; the implications of the findings are discussed in relation to the crossbridge cycle. The data indicate that the endothermic, entropy driven process that underlies crossbridge force generation in isometric muscle (Zhao and Kawai 1994; Davis, 1998) is even more pronounced in shortening muscle, i.e. when doing external work.

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Temperature dependence of isotonic force from isotonic release experiments. A re-analysis of previous experimental data on the force–shortening velocity relation at different temperatures (Ranatunga 1984); this study, on a rat fast muscle, measured the shortening velocity at different constant isotonic force levels (the isotonic release method) at 10, 15, 20, 25, 30 and 35°C. (a) Using the mean data defining the normalised force versus shortening velocity curves for various temperatures (a/P0 ratio of Hill’s equation and Vmax, see Table 1 in Ranatunga 1984) and the ~2-fold (sigmoidal) increase of isometric force on warming from 10 to 35°C (Ranatunga and Wylie 1983; Coupland and Ranatunga 2003), the isotonic force at 5 different shortening velocities (range 0.25–5 L0/s) were calculated for different temperatures. The computed isotonic force (symbols) at the 5 shortening velocities and the isometric force (filled squares) are plotted, as a ratio of isometric force at 35°C, against reciprocal absolute temperature; a sigmoidal curve is fitted to the set of data for a given velocity. Note that, force increases with increase of temperature in all cases and, with increase of velocity (from right to left), the sigmoidal curves are shifted to higher temperatures - as obtained with ramp shortening (Fig. 3a). (b) The linear van’t Hoff plots made on the data; the slope of the linear regression increases with velocity so that ∆H increases from ~125 kJ mol−1 for isometric to ~220 kJ mol−1 for velocity of ~5 L0/s; ∆S increases from ~400 J mol−1 K−1 to ~750 J mol−1 K−1, basically similar to the findings from ramp shortening (Fig. 3c)
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Fig4: Temperature dependence of isotonic force from isotonic release experiments. A re-analysis of previous experimental data on the force–shortening velocity relation at different temperatures (Ranatunga 1984); this study, on a rat fast muscle, measured the shortening velocity at different constant isotonic force levels (the isotonic release method) at 10, 15, 20, 25, 30 and 35°C. (a) Using the mean data defining the normalised force versus shortening velocity curves for various temperatures (a/P0 ratio of Hill’s equation and Vmax, see Table 1 in Ranatunga 1984) and the ~2-fold (sigmoidal) increase of isometric force on warming from 10 to 35°C (Ranatunga and Wylie 1983; Coupland and Ranatunga 2003), the isotonic force at 5 different shortening velocities (range 0.25–5 L0/s) were calculated for different temperatures. The computed isotonic force (symbols) at the 5 shortening velocities and the isometric force (filled squares) are plotted, as a ratio of isometric force at 35°C, against reciprocal absolute temperature; a sigmoidal curve is fitted to the set of data for a given velocity. Note that, force increases with increase of temperature in all cases and, with increase of velocity (from right to left), the sigmoidal curves are shifted to higher temperatures - as obtained with ramp shortening (Fig. 3a). (b) The linear van’t Hoff plots made on the data; the slope of the linear regression increases with velocity so that ∆H increases from ~125 kJ mol−1 for isometric to ~220 kJ mol−1 for velocity of ~5 L0/s; ∆S increases from ~400 J mol−1 K−1 to ~750 J mol−1 K−1, basically similar to the findings from ramp shortening (Fig. 3c)

Mentions: In a previous study (Ranatunga 1984), we examined the force–shortening velocity relation in rat fast (extensor digitorum longus) muscle using the isotonic release method, where the steady velocity was measured at constant force levels and data defining the force–velocity curve were obtained for temperatures ranging from 10 to 35°C; the isometric force increase in warming from 10 to 35°C was ~2-fold (Ranatunga and Wylie 1983), as found in the previous (Coupland and Ranatunga 2003) and present experiments on fast FHB fibres. It is therefore of interest to re-analyse the data from those isotonic release experiments to determine, for a number of shortening velocities, the temperature dependence of isotonic force. This was done using the mean data for the normalised force–velocity curves given in Table 1 in Ranatunga (1984) and temperature-dependence of P0 given in Fig. 3b in Coupland and Ranatunga (2003). From these reanalyses, the data for isometric (filled squares) and five shortening velocities (0.25–5 L0/s) are shown in Fig. 4a where the presentation is similar to Figs. 3a, 4b shows the vant Hoff’s plots of the same data. The basic features described for the temperature dependence of force in ramp shortening experiments (Fig. 3) are also seen in the isotonic release experimental data (Fig. 4).Fig. 4


An analysis of the temperature dependence of force, during steady shortening at different velocities, in (mammalian) fast muscle fibres.

Roots H, Ranatunga KW - J. Muscle Res. Cell. Motil. (2008)

Temperature dependence of isotonic force from isotonic release experiments. A re-analysis of previous experimental data on the force–shortening velocity relation at different temperatures (Ranatunga 1984); this study, on a rat fast muscle, measured the shortening velocity at different constant isotonic force levels (the isotonic release method) at 10, 15, 20, 25, 30 and 35°C. (a) Using the mean data defining the normalised force versus shortening velocity curves for various temperatures (a/P0 ratio of Hill’s equation and Vmax, see Table 1 in Ranatunga 1984) and the ~2-fold (sigmoidal) increase of isometric force on warming from 10 to 35°C (Ranatunga and Wylie 1983; Coupland and Ranatunga 2003), the isotonic force at 5 different shortening velocities (range 0.25–5 L0/s) were calculated for different temperatures. The computed isotonic force (symbols) at the 5 shortening velocities and the isometric force (filled squares) are plotted, as a ratio of isometric force at 35°C, against reciprocal absolute temperature; a sigmoidal curve is fitted to the set of data for a given velocity. Note that, force increases with increase of temperature in all cases and, with increase of velocity (from right to left), the sigmoidal curves are shifted to higher temperatures - as obtained with ramp shortening (Fig. 3a). (b) The linear van’t Hoff plots made on the data; the slope of the linear regression increases with velocity so that ∆H increases from ~125 kJ mol−1 for isometric to ~220 kJ mol−1 for velocity of ~5 L0/s; ∆S increases from ~400 J mol−1 K−1 to ~750 J mol−1 K−1, basically similar to the findings from ramp shortening (Fig. 3c)
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2493522&req=5

Fig4: Temperature dependence of isotonic force from isotonic release experiments. A re-analysis of previous experimental data on the force–shortening velocity relation at different temperatures (Ranatunga 1984); this study, on a rat fast muscle, measured the shortening velocity at different constant isotonic force levels (the isotonic release method) at 10, 15, 20, 25, 30 and 35°C. (a) Using the mean data defining the normalised force versus shortening velocity curves for various temperatures (a/P0 ratio of Hill’s equation and Vmax, see Table 1 in Ranatunga 1984) and the ~2-fold (sigmoidal) increase of isometric force on warming from 10 to 35°C (Ranatunga and Wylie 1983; Coupland and Ranatunga 2003), the isotonic force at 5 different shortening velocities (range 0.25–5 L0/s) were calculated for different temperatures. The computed isotonic force (symbols) at the 5 shortening velocities and the isometric force (filled squares) are plotted, as a ratio of isometric force at 35°C, against reciprocal absolute temperature; a sigmoidal curve is fitted to the set of data for a given velocity. Note that, force increases with increase of temperature in all cases and, with increase of velocity (from right to left), the sigmoidal curves are shifted to higher temperatures - as obtained with ramp shortening (Fig. 3a). (b) The linear van’t Hoff plots made on the data; the slope of the linear regression increases with velocity so that ∆H increases from ~125 kJ mol−1 for isometric to ~220 kJ mol−1 for velocity of ~5 L0/s; ∆S increases from ~400 J mol−1 K−1 to ~750 J mol−1 K−1, basically similar to the findings from ramp shortening (Fig. 3c)
Mentions: In a previous study (Ranatunga 1984), we examined the force–shortening velocity relation in rat fast (extensor digitorum longus) muscle using the isotonic release method, where the steady velocity was measured at constant force levels and data defining the force–velocity curve were obtained for temperatures ranging from 10 to 35°C; the isometric force increase in warming from 10 to 35°C was ~2-fold (Ranatunga and Wylie 1983), as found in the previous (Coupland and Ranatunga 2003) and present experiments on fast FHB fibres. It is therefore of interest to re-analyse the data from those isotonic release experiments to determine, for a number of shortening velocities, the temperature dependence of isotonic force. This was done using the mean data for the normalised force–velocity curves given in Table 1 in Ranatunga (1984) and temperature-dependence of P0 given in Fig. 3b in Coupland and Ranatunga (2003). From these reanalyses, the data for isometric (filled squares) and five shortening velocities (0.25–5 L0/s) are shown in Fig. 4a where the presentation is similar to Figs. 3a, 4b shows the vant Hoff’s plots of the same data. The basic features described for the temperature dependence of force in ramp shortening experiments (Fig. 3) are also seen in the isotonic release experimental data (Fig. 4).Fig. 4

Bottom Line: In shortening, these were increased with increase of velocity so that at a shortening velocity (approximately 4 L(0)/s) producing maximal power at 35 degrees C, T(0.5) was approximately 28 degrees C, DeltaH was approximately 200 kJ mol(-1) and DeltaS approximately 700 J mol(-1) K(-1); the same trends were seen in the tension data from isotonic release experiments on intact muscle and in ramp shortening experiments on maximally Ca-activated skinned fibres.In general, our findings show that the sigmoidal relation between force and temperature can be extended from isometric to shortening muscle; the implications of the findings are discussed in relation to the crossbridge cycle.The data indicate that the endothermic, entropy driven process that underlies crossbridge force generation in isometric muscle (Zhao and Kawai 1994; Davis, 1998) is even more pronounced in shortening muscle, i.e. when doing external work.

View Article: PubMed Central - PubMed

Affiliation: Muscle Contraction Group, Department of Physiology & Pharmacology, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.

ABSTRACT
We examined, over a wide range of temperatures (10-35 degrees C), the isometric tension and tension during ramp shortening at different velocities (0.2-4 L(0)/s) in tetanized intact fibre bundles from a rat fast (flexor hallucis brevis) muscle; fibre length (L(0)) was 2.2 mm and sarcomere length approximately 2.5 microm. During a ramp shortening, the tension change showed an initial inflection of small amplitude (P(1)), followed by a larger exponential decline towards an approximate steady level; the tension continued to decline slowly afterwards and the approximate steady tension at a given velocity was estimated as the tension (P(2)) at the point of intersection between two linear slopes, as previously described (Roots et al. 2007). At a given temperature, the tension P(2) declined to a lower level and at a faster rate (from an exponential curve fit) as the shortening velocity was increased; the temperature sensitivity of the rate of tension decline during ramp shortening at different velocities was low (Q(10) 0.9-1.5). The isometric tension and the P(2) tension at a given shortening velocity increased with warming so that the relation between tension and (reciprocal) temperature was sigmoidal in both. In isometric muscle, the temperature T(0.5) for half-maximal tension was approximately 10 degrees C, activation enthalpy change (DeltaH) was approximately 100 kJ mol(-1) and entropy change (DeltaS) approximately 350 J mol(-1) K(-1). In shortening, these were increased with increase of velocity so that at a shortening velocity (approximately 4 L(0)/s) producing maximal power at 35 degrees C, T(0.5) was approximately 28 degrees C, DeltaH was approximately 200 kJ mol(-1) and DeltaS approximately 700 J mol(-1) K(-1); the same trends were seen in the tension data from isotonic release experiments on intact muscle and in ramp shortening experiments on maximally Ca-activated skinned fibres. In general, our findings show that the sigmoidal relation between force and temperature can be extended from isometric to shortening muscle; the implications of the findings are discussed in relation to the crossbridge cycle. The data indicate that the endothermic, entropy driven process that underlies crossbridge force generation in isometric muscle (Zhao and Kawai 1994; Davis, 1998) is even more pronounced in shortening muscle, i.e. when doing external work.

Show MeSH
Related in: MedlinePlus