Improvement of the measurements on skinned muscle fibres by fixation of the fibre ends with glutaraldehyde.

Experiments with activated skinned muscle fibre segments are limited by the structural and mechanical instability of the preparations. The present study shows that fixation of the muscle fibre ends with glutaraldehyde significantly improves the reliability of such experiments. We tested the effects of a specific glutaraldehyde fixation technique on the structural stability and the mechanical properties of skinned rat and rabbit skeletal muscle fibres in an approach where the fibre segments are attached to the apparatus by gluing. Preparations with fixed and unfixed ends were compared. During the first few minutes of maximal activation, fibres with fixed and unfixed ends exhibited similar mechanical properties to one another, suggesting that our fixation procedure selectively impregnates the fibre ends without contaminating the remaining active fibre part. During prolonged maximal activations (3-60 min), preparations with fixed ends exhibited a better stability, both in the sarcomere length signal (detected by laser diffraction) and in the unloaded shortening velocity. Thus, our technique of muscle fibre end fixation caused a substantial improvement in the mechanical measurements on skinned muscle preparations.