Fixation and immunofluorescent analysis of creatine kinase isozymes in embryonic skeletal muscle

Pectoral muscles from chicken embryos of various ages were examined with immunofluorescent and radiolabeled probes for the presence of brain-type creatine kinase (B-CK), muscle-specific creatine kinase (M-CK), muscle-specific myosin heavy chain (MHC), and cycling cells. The diffusible creatine kinase isozymes were not detectable by indirect immunofluorescence after standard histological fixation of embryonic muscle. However, a fixation procedure was devised that permitted immunodetection of the creatine kinase isozymes (particularly B-CK) in embryonic tissue from all stages of development studied. B-CK, M-CK, and MHC were all detected in post-mitotic muscle cells, but only B-CK was detected in cycling cells. Correlations between these findings and in vitro observations of a deterministic muscle lineage are discussed.