Metabolism of myofibrillar proteins in the normal and hypertrophic heart

Abstract

The pathways of myofibrillar assembly and degradation were studied in normal heart and during developing hypertrophy by two independent methods: amino acid incorporation kinetics and the double isotope technique. The validity and sensitivity of both methods were evaluated by computer analysis of data for which leucyl-tRNA was used as a protein precursor. The data obtained indicate that the myofibrillar proteins turn over at nonuniform rates. The half-lives of the proteins studied increase as follows: myosin HC = alpha-actin = tropomyosin greater than LC1 = LC2 greater than actin. In the case of light chains, a macromolecular precursor pool was detected which contributes to the observed lower labeling with 3H-leucine. During developing hypertrophy, the rate of light-chain labeling is increased relative to that of heavy chains.