FIBER-TYPE SPECIFIC EXPRESSION OF LEU19-ANTIGEN AND N-CAM IN SKELETAL-MUSCLE IN VARIOUS STAGES AFTER EXPERIMENTAL DENERVATION

Leu-19 antigen, which seems to be identical with neural cell adhesion molecule (N-CAM), plays a major role in the innervation of muscle cell s, and in adult muscle appears after denervation and during regenerati on of muscle fibres, where it acts as part of a signalling system incr easing the probability of re-innervation. This combined enzyme-histoch emical and immunohistochemical study examined whether this signalling process was regulated in a uniform or differential pattern for type 1 and type 2 muscle fibres. The subscapular nerve of 18 rabbits was tran ssected with subsequent complete denervation of the supraspinatus musc le. Leu-19 and N-CAM immunohistochemistry was performed 2 to 64 days a fter surgery. Whereas in normal muscle there are virtually no Leu-19/N -CAM positive muscle fibres; from day 2 after denervation an increasin g proportion of fibres expressed Leu-19/N-CAM, prior to any neurogenic atrophy. In the early stage of denervation Leu19/N-CAM expression was confined to type 1 fibres. After 11 days nearly all fibres were Leu19 /N-CAM positive irrespective of their fibre type. Sixty-four days afte r denervation type 1 fibres became Leu19/N-CAM negative, while atrophi c type 2 fibres showed intensive staining. Thus, expression of Leu-19 antigenity is differently regulated in both fibre types.