A new method for myofibrillar Ca++-ATPase reaction based on the use of metachromatic dyes: its advantages in muscle fibre typing.

A new method for Ca++-ATPase reaction in human muscle fibres is presented as an alternative to previous ATPase stains. The method is based on the use of metachromatic dyes, namely Azure A and Toluidine Blue, and has the advantages of speed, ease of performance and production of an elegant and clearcut fibre typing. The method distinguishes fibre types because of their metachromatic or orthochromatic staining, due to their different content of phosphate after incubation in the reaction medium. The comparison of serial sections stained by cationic dyes and by ammonium sulphide revealed close correspondence of fibre typing. Fibre type differentiation was also obtained with Acridine Orange; however this method was less reproducible.