THE USE OF P-33 LABELED RIBOPROBES FOR IN-SITU HYBRIDIZATIONS - LOCALIZATION OF MYOSIN ALKALI LIGHT-CHAIN MESSENGER-RNAS IN ADULT HUMAN SKELETAL-MUSCLE

P-33-labelled probes were used to localize the mRNAs coding for the my osin alkali light-chain isoforms MLC 1f/3f and MLC 1sb in adult human muscles, which are distributed in characteristic fibre type specific p atterns. In situ hybridizations of P-33-labelled probes were compared with probes carrying S-35 or digoxigenin labels. Signals of equal stre ngth were obtained with each of the three labels. The preferentially p eripheral localization of these mRNAs in the muscle fibres could be cl early seen with all three probes, with digoxigenin probes providing th e best resolution. P-33 can serve as a viable alternative in this type of experiment. These experiments with adult human muscles also showed that the post mortem stability of RNA in human muscle is better than generally assumed. We could detect no signs of degradation in RNA prep ared from heart ventricle as well as skeletal muscle up to 24 hours po st mortem. In situ hybridizations worked equally well in biopsy materi al as in post mort em samples.