Histochemical observations on creatine phosphokinase activity in the red and white fibres of normal and denervated pigeon breast muscle

Abstract

Creatine phosphokinase activity in the red (Type I) and white (Type II) fibres of pigeon breast muscle was found to be localized in the mitochondria. In the normal muscle the activity of the enzyme was found to be considerably greater in the red fibres than in the white. In 7-day denervated muscle there was a significant increase of enzyme activity in the white fibres while no perceptible change could be noticed in the red fibres. In 30-day denervated muscle there was a striking reduction in the diameter of the white fibres which were found to be more susceptible to atrophy. Those of the white fibres which still retained their cellular integrity, showed a deeper staining reaction for the activity of this enzyme than the red fibres, though the intensity of staining in both fibre types was considerably less than that in the normal or in the 7-day denervated muscle. It is suggested that the mitochondria of the white fibres undergo a temporary functional hypertrophy during the early period of denervation atrophy of the muscle and that these changes are controlled by the influence of the motor nerve.