Regulation of taurine transport in rat skeletal muscle

Taurine concentration of soleus muscle (SL, slow-twitch) was initially about twofold higher than that of extensor digitorum longus muscle (EDL, fast-twitch). Taurine concentration in gastrocnemius muscle (GC) was intermediate between that of EDL and SL. Four days after sciatic nerve section, taurine concentration in the EDL but not in the SL was increased by 2.5-fold. The increase was not due to the muscle atrophy and was observed 28 days after denervation. Tenotomy did not increase the total taurine content of the EDL. The increase in taurine concentration of the denervated EDL was prevented by simultaneous ingestion of guanidinoethane sulfonate, a competitive inhibitor of taurine transport. The initial and the maximal rates of [3H]taurine uptake were significantly higher in SL than in EDL. Denervation dramatically accelerated the initial and the maximal rates of the transport in EDL, whereas it significantly reduced those in SL. In contrast, the electrical stimulation of sciatic nerve accelerated the uptake of taurine by EDL and SL of the control but not of the curare-treated rats. These results suggest that transport of taurine into rat skeletal muscles is regulated differently by neural information and by muscular activity, and that the regulation is dependent on the muscle phenotype.