Protein metabolism in slow- and fast-twitch skeletal muscle during turpentine-induced inflammation

Abstract

The aim of our study was to evaluate the differences in protein and amino acid metabolism after subcutaneous turpentine administration in the soleus muscle (SOL), predominantly composed of red fibres, and the extensor digitorum longus muscle (EDL) composed of white fibres. Young rats (40-60 g) were injected subcutaneously with 0.2 ml of turpentine oil/100 g body weight (inflammation) or with the same volume of saline solution (control). Twenty-four hours later SOL and EDL were dissected and incubated in modified Krebs-Heinseleit buffer to estimate total and myofibrillar proteolysis, chymotrypsin-like activity of proteasome (CHTLA), leucine oxidation, protein synthesis and amino acid release into the medium. The data obtained demonstrate that in intact rats, all parameters measured except protein synthesis are significantly higher in SOL than in EDL. In turpentine treated animals, CHTLA increased and protein synthesis decreased significantly more in EDL. Release of leucine was inhibited significantly more in SOL. We conclude that turpentine-induced inflammation affects more CHTLA, protein synthesis and leucine release in EDL compared to SOL.

Figure 1

Relative effect of inflammation on basic parameters of protein and amino acid metabolism in EDL (filled bars) and SOL (open bars). Means of appropriate control values were used as 100%. Values are means ± SEM, n = 7 in each group. F-test followed by two-sample t-test; ^•P < 0.05 vs. EDL. SOL, the soleus muscle; EDL, the extensor digitorum longus muscle; CHTLA, chymotrypsin-like activity.

Figure 2

Relative effect of inflammation on amino acid release from EDL (filled bars) and SOL (open bars). Means of appropriate control values were used as 100%. Values are means ± SEM, n = 7 in each group. F-test followed by two-sample t-test; ^•P < 0.05 vs. EDL. SOL, the soleus muscle; EDL, the extensor digitorum longus muscle; BCAA, branched chain amino acids (valine, leucine, isoleucine); TOTAL, sum of all measured amino acids; ALA, ASN, GLU, GLN, GLY, HIS, ILE, LEU, LYS, MET, PHE, PRO, SER, VAL – standard amino acid abbreviations.