Protein Growth and Synthesis in Tissues

Houlihan and Laurent 1987 Houlihan et al. 1988b). The fractional rates of protein synthesis of white muscle are the most responsive to the nutritional state of the fish (Fauconneau et al. 1981 Smith 1981 Lied et al. 1985) in cod it increases over sevenfold with increasing growth rates and demonstrates the closest relationship with growth rate. 

The different muscle fibre types of fish may be cited as examples of tissues with widely differing fractional protein synthesis rates cardiac muscle has often been found to have fractional protein synthesis rates which are approximately four fold higher than those of white muscle fibres (Haschemeyer et al. 1979 Smith et al. 1980 Fauconneau 1985 Houlihan et al. 1986 Houlihan et al. 1988b McMillan and Houlihan 1988). 

Isolated trout hearts have been used to study the effects of changes of power output on the rates of protein synthesis (Houlihan et al. 1988a). In vitro the different chambers of the heart have markedly different fractional rates of protein synthesis the atrium seems to be particularly sensitive to the input pressure applied to the heart. Increasing cardiac power output twofold increased the fractional rates of protein synthesis in both the atrium and ventricle but not in the bulbus arteriosus (Fig. 12). However, a cautionary note must be added in that the ranking of fractional rates of protein synthesis of the heart chambers found in vitro was not repeated in vivo. However, it is likely that the power output-related fractional rates of protein synthesis found in vitro are also occurring in vivo slow speed continuous swimming stimulates trout cardiac protein synthesis and this may be part of the 

We have taken the analysis of protein synthesis in the trout heart further by looking at the types of proteins that are synthesised. Firstly, fractionation of the trout ventricle after incubation in vivo presents a uniform picture of the rates of protein synthesis in the various fractions (Fig. 13). Results from crude subcellular fractionation of rat ventricle have also pointed to similar fractional rates of protein synthesis in different fractions (Preedy et al. 1985). When absolute rates of protein synthesis are calculated, the myofibrillar fraction turns out to be the major site of protein synthesis. 

Work on in vitro rates of protein synthesis in mammals has been characterised by much lower rates of synthesis compared with in vivo rates (Palmer et al. 1981 Goldspink et al. 1984). Recently, Wrigley and Ash (1989) have highlighted the problems using isolated fish muscle for the measurement of protein turnover. We have already found that perfusion of the coronary vessels of the trout ventricle significantly improves performance and the rates of protein synthesis in the compact layer of the ventricle supplied by these vessels (Houlihan et al. 1988a) possible variations in in vitro methodology have recently been discussed (Perry and Farrell 1989). 

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