Acid phosphatase activity in soleus and plantaris muscle fibres of normal and dystrophic hamsters. A quantitative histochemical study

Characterization of alkaline and acid phosphatases from skeletal muscles of young and old rats

Alkaline phosphatase (ALP) and acid phosphatase (ACP) specific activities were measured in gastrocnemius muscles of female Wistar rats ranging in age from 2 to 30 months. ALP activity reached a peak at 12 months, with a subsequent slow decline with age. ACP activity increased sharply up to 12 months of age, followed by a slower elevation up to the age of 30 months. Using histochemical staining techniques and electron microscopy, the presence of ALP was demonstrated in the sarcolemma of gastrocnemius muscles, as well as in some capillaries around muscle fibers. ALP and ACP were isolated further from muscles of young (12 months) and old (30 months) animals by applying ion-exchange chromatography and separation on a Sephadex G-200 column. The purity of ALP was shown on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). From a calibrated Sephadex G-200 column and SDS-PAGE, the molecular mass of ALP was determined as 116 kilodaltons (kDa), a dimer of two 56-kDa monomers. The ACP major peak of the Sephadex G-200 column revealed a molecular mass of 40 kDa. No differences in molecular mass or in amino acid analysis were detected between ALP(s) from young and old animals, indicating that most probably the decline of activity with age is due to some post-translational events, as has been shown in the past for many other enzymes and proteins.

Dipeptidyl peptidases in the soleus muscle of the rat before and after treatment with 5-hydroxytryptamine

A moderate peptidase activity against L-lysyl-L-proline-4-methoxy-beta-napththylamide was detected histochemically in unfixed sections of soleus muscle fibres of inbred male Wistar rats using two variants of the semipermeable membrane technique. One variant involved simultaneous coupling with tetrazotised 3,3'-dimethoxybenzidine, the other post-coupling. The activity at pH 6 increased approximately three-fold in many fibres showing signs of insult in rats that had been given a single low dose of 5-hydroxytryptamine (10 mg/kg body weight) 48-72 h earlier. The hydroxytryptamine treatment was found to induce a selective myopathy. Some of the increased peptidase activity within insulted muscle fibres appeared to arise from invading mononuclear cells, but the majority seemed endogenous to muscle fibres. The peptidase activity persisted in some fibres 21-28 days after 5-hydroxytryptamine administration, by which time the whole muscle appeared histologically normal. The variation of the activity of the peptidase with pH in the presence of various inhibitors was investigated in both control and insulted muscle fibres. From its sensitivity and behaviour towards Zn2+, Hg2+, Cu2+, puromycin, benzethonium chloride and phenylmethylsulphonyl fluoride and its indifference towards Co2+, Cd2+, Mn2+ and o-phenanthroline, it is concluded that the activity can be attributed to a mixture of at least two peptidases, dipeptidyl peptidase II and an unidentified neutral dipeptidyl peptidase. The possible role of the peptidase(s) in muscle regeneration in discussed.