Contractile proteins are coordinately expressed during myogenesis. It is unclear how cellular control of these protein levels is achieved so that the components are assembled with the appropriate stoichiometry. A specific muscle gene was selectively blocked to examine the effects of disrupting such coordinated regulation. The slow/cardiac isoform of troponin C (s/cTnC) was efficiently inhibited using antisense oligomers. As low as 1 [mu]M phosphorothioate (PS) oligodeoxyribonucleotide was required to notably reduce the level of s/cTnC synthesis, however substantially greater concentrations of phosphodiester (PO) were needed to attain similar inhibition. Of the various s/cTnC mRNA targeted regions, the 51 cap sequence was found to be the most effective site for blocking expression. Use of sense and scrambled counterparts of the 51 cap sequence, as well as an unrelated mRNA contractile protein target, indicated that the observed changes in s/cTnC protein levels were not a result of non-antisense mechanisms. While the use of antisense oligomers successfully reduced the levels of s/cTnC protein synthesis and steady state levels, the capacity of the muscle cells to contract was not examined. As the troponin C polypeptide plays an essential role in the contraction process, knowledge of its regulatory mechanisms may provide insight into the cause of certain myopathies. (Abstract shortened by UMI.)