MUSCLE-SPECIFIC ENZYME-ACTIVITY PATTERNS OF THE CAPILLARY BED OF HUMAN OROFACIAL, MASTICATORY AND LIMB MUSCLES

Enzyme-histochemical methods were used to analyse the activities of al kaline phosphatase (AP), dipeptidylpeptidase IV (DPP IV) and adenosine triphosphatase (ATPase) in capillaries of four different human oro-fa cial muscles, the major and minor zygomatic, the orbicularis oris and buccinator, one masticatory, the masseter and two limb muscles, the bi ceps brachii and first dorsal interosseus muscles. In all muscles, exc ept for the orbicularis oris, the majority of the capillaries lacked e nzyme activity. Therefore, none of these enzymes seems to be reliable as a general marker for human muscle capillaries. In general, the capi llaries of the limb muscles and the major and minor zygomatic and the buccinator, were similar in their staining pattern for AP and ATPase, but differed in DPP IV staining. The orbicularis oris muscle differed from the other muscles by showing the largest proportion of capillarie s with AP and ATPase activity. The masseter muscle had the largest pro portion of capillaries stained for DPP IV. The muscle specific differe nces in enzyme activity of the capillaries are in agreement with our p revious findings of specific differences between limb, oro-facial and masticatory muscles with respect to capillary supply and composition o f fibre types and myosins. The results reflect functional specializati on of the capillary bed of human muscles.