Effect of taurine on sarcoplasmic reticulum function and force in skinned fast‐twitch skeletal muscle fibres of the rat

Abstract

We examined the effect of taurine on depolarisation-induced force responses and sarcoplasmic reticulum (SR) function in mechanically skinned skeletal muscle fibres from the extensor digitorum longus (EDL) of the rat. Taurine (20 mm) produced a small but significant (P < 0.01) decrease in the sensitivity of the contractile apparatus to Ca²⁺ (increase in the [Ca²⁺] corresponding to 50 % of maximum force of about 7 %; n= 10) and in maximum force (92.0 ± 1.0 % of controls) in the skinned fibres. Taurine had no statistically significant effect on the slope of the force-pCa curve. Depolarisation-induced force responses in the skinned fibres were markedly increased in peak value by 20 mm taurine, to 120.8 ± 5.3 % of control measurements (P= 0.0006, n= 27). Taurine (20 mm) significantly increased the SR Ca²⁺ accumulation in the skinned fibres by 34.6 ± 9.3 % compared to control conditions (measured by comparing the integral of caffeine contractures in fibres previously loaded with Ca²⁺ in the absence or presence of taurine; P= 0.0014, n= 10). Taurine (20 mm) also increased both the peak and rate of rise of caffeine-induced force responses in the fibres by 29.2 ± 9.7 % (P= 0.0298, n= 6) and 27.6 ± 8.9 % (P= 0.037), respectively, compared with controls. This study shows that taurine is a modulator of contractile function in mammalian skeletal muscle. Taurine may increase the size of depolarisation-induced force responses by augmenting SR Ca²⁺ accumulation and release.