Dichroic components of Arsenazo III and dichlorophosphonazo III signals in skeletal muscle fibres

1. Absorbance changes were measured following stimulation of single muscle fibres injected with the metallochromic indicator dye Arsenazo III. Two dye‐related signals can be clearly resolved: (1) an early, transient isotropic signal that appears to be due to the formation of Ca2+:dye complex and (2) a slower, transient signal that is ‘dichroic’ in nature. The dichroic signal is obtained by taking the difference between absorbance changes measured with light plane polarized along the fibre axis (0° light) and at right angles to the axis (90° light).