Transient phases of the isometric tetanus in frog’s striated muscle

Abstract

In an isometric tetanus in frog’s sartorius muscle tension approaches the plateau exponentially with rate constant α. α depends on sarcomere length, s, and temperature, T, according to the Arrhenius equation α(s, T) = A(s) esp [- E/R(1/T - 3.4 × 10-3)] for temperatures between 1 and 20°C and for sarcomere lengths 2.0-2.8 µm. The energy of activation, E, does not vary significantly with s; E = 13.9 ± 2.4 kcal/mole. A(s) decreases monotonically with s; A(2.1 µm) is about three times greater than A(2.8 µm). Late in relaxation active tension approaches zero exponentially with rate constant r. r decreases exponentially with increasing duration of tetanus, D, from r0 in a twitch to r∞ for large D. The rate constant for decrease of r with D increases with s and with T. r0 and r∞ obey the Arrhenius equation and decrease with increasing s. © 1971, Rockefeller University Press., All rights reserved.