Long-term alcohol administration inhibits synthesis of both myofibrillar and sarcoplasmic proteins in heart.

Alcohol decreases the rate of protein synthesis in cardiac muscle. We investigated the effects of feeding rats a diet containing alcohol for 16 weeks on the myocardial synthesis of myofibrillar and sarcoplasmic (non-myofibrillar) proteins. Alcohol administration decreased the overall rate of protein synthesis in cardiac muscle by 22% compared with controls (P < .05). The rate of synthesis of proteins in the myofibrillar and sarcoplasmic fractions was diminished proportionately after feeding a diet containing alcohol (P < .05). We examined the effects of diminished rates of protein synthesis on the expression of myofibrillar and non-myofibrillar proteins. The cellular content of actin and alpha -myosin heavy chain isoform was significantly reduced and there was an increase in the beta -myosin heavy chain isoform after feeding rats a diet containing alcohol. The reduced expression of myosin heavy chain isoform and actin did not result from a decreased abundance of messenger RNA for either of these proteins. The myocardial content of troponin C and T was unchanged whereas that of troponin I was increased. Ethanol administration reduced the expression of eEF2 and the inducible form of the 70-kDa heat shock protein, whereas the cognate form of the 70-kDa heat shock protein was unaffected in a non-myofibrillar-enriched fraction of cardiac muscle. These results suggest that (1) the reduced protein content observed in the heart after feeding a diet containing alcohol is a consequence of reduced synthesis of both myofibrillar and sarcoplasmic proteins, and (2) the expression of both actin and alpha-myosin heavy chain isoform is affected independently of the messenger RNA content of the proteins. We conclude that translational control mechanisms appear to be important in regulating the expression of myocardial proteins during long-term ethanol intoxication.