Acta Biochimica et Biophysica 11. (1976)

1976 / 4. szám - Lőrinczi, D.-Tigyi, J.: Dependence of the Heatproduction of Active Muscle of the Length of Muscle

Acta Biochim. et Biophys. Acad. Sei. Hung. Vol. 11 (4), pp. 311—321 (1976) Dependence of the Heat Production of Active Muscle on the Length of Muscle D. LŐRINCZI, J. TlGYI Biophysical Institute, Medical University, Pécs (Received December 24, 1975) The dependence of the heat production of muscle on length was examined in isometric (with stretch) and isotonic (free of stretch) tetanuses of 2 s. The isometric heat production was significantly greater than the isotonic one at any length of muscle. The isometric heat coefficient (FIJQ, where F is the active tension development of muscle measured in ponds, /„ is the resting length measured in cm, Q is the heat production during the contraction at a given length measured in meal) was not con­stant but depended on the length of muscle, and had an extreme value near the resti ng length (/„). A close positive correlation was found between the active tension development and the heat production of the muscle. Introduction As to the extent of heat phenomena accompanying muscular activity it is widely accepted that heat production is greater in isotonic than in isometric con­traction (Fenn, 1923, 1924; Hill, 1930, 1965; Woledge, 1968; Fales, 1969b; Dickinson, Woledge, 1974). In the case of isometric contractions at different initial lengths the active tension development and heat production of muscle have a maximum near the resting length, and they change almost parallel with each other (Hill, 1958). For isometric heat coefficient Hill (1928, 1958) obtained a constant value which was independent of length (FIJQ, where F is the active tension development of the muscle measured in grams in his experiment, /0 is the resting length measured in cm, Q is the heat production during a contraction at a given length measured in gem). Its value changed within a wide range as the methods of measurement became more perfect. Values in the case of twitch are : 6.16 (Hill, 1928), 8.25 (Rosen­berg, 1934)and 10.3 (Hill, 1958). Fales etal. (1967) corroborated Hill'sresults on the dependence of the heat production of muscle on length with the so-called gradient­­layer calorimetry, a method entirely independent from the one used by Hill. Active tension development and heat production take place almost parallelly during twitches and, at 0.8 l0 as well as 1.2 /„, they differ from the value measured at resting length by almost 25 per cent. Their result of 11.5 obtained from isometric heat coefficient is also in accordance with previous experiments. For Acta Biochimica et Biophysica Academiae Scientiarum Hungaricae 11, 1976

Next