Acid hydrolases in normal and diseased human muscle

Beta Adrenoceptor Agonists, Clenbuterol, and Isoproterenol Retard Denervation Atrophy in Rat Gastrocnemius Muscle: Use of 3-Methylhistidine as a Marker of Myofibrillar Degeneration

The effects of beta adrenergic agonists, clenbuterol (2 mg/kg body weight/d) and isoproterenol (12 mg/kg body weight/d), in normal innervated and denervated rat gastrocnemius muscle were investigated. The daily administration of beta adrenergic agonists to normal innervated rats for a short period (7 d) resulted in the hypertrophy of gastrocnemius as confirmed from the measurement of total tissue protein contents. The development of denervation atrophy witnessed a stimulation in the expression of acid and alkaline phosphatases, pointing to an enhanced myofibrillar degeneration. An administration of beta adrenergic agonists inhibited the expression of raised levels of these enzymes in denervated muscle. A measurement of 3-methylhistidine in muscle revealed a loss of amino acid with the progress in the development of denervation atrophy. Serum and urine samples from denervated rats showed a progressive accumulation of 3-methylhistidine. Clenbuterol and isoproterenol treatment to these rats resulted in an inhibition of 3-methylhistidine accumulation. When 3-methylhistidine was used as a marker of myofibrillar degeneration, the results seemed to suggest that the degeneration of cyto-contractile apparatus accompanying denervation atrophy is attenuated in the presence of beta adrenergic agonists, implying that these sympathomimetic drugs are capable of reversing denervation atrophy in rat gastrocnemius.

Skeletal muscle metabolism in mice bearing adenocarcinoma. II. Histochemical alterations in acid and alkaline phosphatases

In Swiss albino mice bearing adenocarcinoma the degree of pathological damage as revealed by the activities of acid and alkaline phosphatases is greater in skeletal muscles closely proximal to the tumor site than in those away from it. Acid and alkaline phosphatases in myofibres of triceps, pectoralis and gastrocnemius muscles show a direct relationship between myofibre necrosis and activities of these phosphatases.

Adenylosuccinase in human muscular dystrophy

The level of adenylosuccinase was measured in muscle from patients with Duchenne and other major forms of progressive muscular dystrophies and certain related neuromuscular diseases. The activity was found to be unaltered in all diseases that were examined.

Methylthioadenosine nucleosidase in normal and dystrophic human muscle

Human skeletal muscle homogenate was found to contain a nucleosidase that catalyzes the hydrolysis of 5'-methylthioadenosine, a known inhibitor of many methyl transfer reactions. When the levels of methylthioadenosine nucleosidase in muscle of patients were compared with those of controls, no significant alterations in its activity were noted in patients with various forms of muscular dystrophies, polymyositis and certain denervating diseases.

Muscle breakdown and lysosomal activation (biochemistry)

Muscle tissue levels of lysosomal catheptic enzymes, such as cathepsins D, A, B1, C, and dipeptidyl peptidase II, were measured in control subjects and patients with muscular dystrophies, polymyositis, and certain denervating diseases. The results show that, in general, the activities of these enzymes are increased in muscles of patients with muscular dystrophies and other diseases. The increases in cathepsin D and autolytic activities are not significant until the late stage of the disease process. Cathepsins A, B1, and C are, however, significantly elevated in mildly affected dystrophic and other diseased muscles. Of these catheptic enzymes, cathepsin B1 displays the highest rise at an early stage, suggesting that it may be one of the rate-controlling enzymes of proteolysis. Dipeptidyl peptidase II is increased slightly in dystrophic and other myopathic muscles but is unchanged in denervated muscle. These data clearly implicate the lysosomal group of proteinases as largely responsible for mediating muscle breakdown in the muscular dystrophies and certain other muscle and neuromuscular diseases in man.

Activity of acid hydrolases in skeletal muscle of untrained, trained and detrained mice of different ages

The activities of p-nitrophenylphosphatase, beta-glucuronidase and beta-N-acetylglucosaminidase from crude skeletal muscle homogenates of 4 and 7 months old mice were assayed after short-term intensive and long-term moderate training and after terminated training. In the older untrained mice the activity of the hydrolases was higher than in the younger mice. The level increased with training and this increase was far more pronounced in the older animals. Cessation of training for 7 and 21 days decreased this activity in the older animals but it was again increased 42 days later and close to the level observed in the trained mice. In young mice 3 days' terminated training increased the activity of the acid hydrolases above the level of the trained animals but after additional 4 and 11 days' terminated training the activity decreased to slightly below that of the trained mice. The changes were most prominent in the activity of beta-glucuronidase and to a lesser extent in that of beta-N-acetylglucosaminidase while p-nitrophenylphosphatase activity was almost unaffected by training or terminated training. The effects of terminated training can be intepreted as representing altered catabolic processes in the turn-over of tissue components of skeletal muscle.

Alkaline phosphatase activity in normal and denervated skeletal muscle

Changes in the specific activity of alkaline phosphatase in the normal and denervated skeltal muscle have been studied both histochemically as well as biochemically for a maximum period of 8 weeks of its postnatal development. In the normal muscle, a heterogenous population of fibres with respect to the enzyme distribution is observed. Relatively higher levels of enzyme in the denervated muscle and also the proliferation of extrafibillar connective tissue in the diseased muscle show its specific association with the lytic processes.

Evaluation of histochemical observations of activity of acid hydrolases obtained with semipermeable membrane techniques: a combined histochemical and biochemical investigation 1. The histochemical investigation

The reliability of enzyme histochemical observations of activities of acid hydrolases was investigated with a combined histochemical and biochemical study. Specimens of m. soleus, m. plantaris, m. gastrocnemius and diaphragm of normal and of vitamin E deficient rabbits were used. For the histochemical investigation, activity and localization of acid phosphatase, beta-glucuronidase, leucine aminopeptidase and E600 resistant non-specific arylesterase were examined with semipermeable membrane techniques. For the biochemical investigation, activity of acid phosphatase, beta-glucuronidase, cathepsin D, acid maltase and neutral maltase was determined. By means of stastical calculations the enzyme activities demonstrated with histochemical techniques were compared with the enzyme activities determined with biochemical techniques. In the present communication the histochemical findings are reported and discussed. From the histochemical findings it appeared that activity of the acid hydrolases investigated is strongly increased in both a granular and a diffuse pattern in skeletal muscle of vitamin E deficient rabbits. The statistical calculations of the histochemical findings clearly reveal that the increased activity of one acid hydrolase was highly significantly paralleled by an increased activity of a second acid hydrolase. Moreover the probability that the activity of all other histochemically studied acid hydrolases was significantly increased was rather high. The increase in activity of the acid hydrolases studied was the same in muscles with an aerobic or an anaerobic metabolism. Moreover there was no difference in activity and localization of the acid hydrolases in aerobic type I and anaerobic type II fibres. The localization of acid phosphatase and beta-glucuronidase activity muscle fibres mostly coincided. In cases where these enzymes were localized both centrally and in the subsarcolemnal areas of the muscle fibres, the activity of E600 resistant naphtholesterase was usually, and the activity of leucine aminopeptidase was exclusively located in the subsarcolemnal areas. All of the examined acid hydrolases were found to be present in the inflammatory exudate and in the connective tissue.

Dipeptidyl peptidases in human muscle disease

With the use of selective inhibitors of arylamidase, four dipeptyl peptidases (I, II, III, and IV) capable of hydrolyzing the beta-naphthylamides of Gly-Arg, Lys-Ala, Arg-Arg and Gly-Pro, respectively, were distinguished in homogenates of human muscle. Dipeptidyl peptidase I showed maximum activity at pH 5.0-6.0. Dipeptidyl peptidase II was maximally active at pH 5.0 and inhibited by cations. Dipeptidyl peptidases III and IV were most active at pH 8.5 and 7.5, respectively. When compared to controls, significant increases in muscle dipeptidyl peptidases I and II were observed in patients with muscular dystrophies and polymyositis. Dipeptidyl peptidase III was not altered in the neuromuscular disease examined. Dipeptidyl peptidase IV showed marked increase in a variety of muscle wasting conditions. The increase in dipeptidyl peptidases I and II may be attributed to lysosomal activation that is known to occur in conditions of muscle degeneration. However, the striking increase in a variety of muscle diseases of dipeptidyl peptidase IV, an enzyme shown to be associated with microsomal membranes in other tissues, suggest that in addition to lysosomes other sources also contribute to the total hydrolytic potential of diseased muscles. Dipeptidyl peptidases II and IV were found to be present in human serum. Their levels were not altered in serum of patients with Duchenne dystrophy.

Acid phosphatase activity in normal and denervated chick skeletal muscle

Histochemical and biochemical changes in acid phosphatase activity were studied in the normal and denervated gastrocnemii of chick for a maximum period of 8 weeks. In the normal muscle, fibre heterogeneity with respect muscles exhibit greater susceptibility to degenerative changes on account of denervation. Quantitatively higher enzyme levels in the denervated muscles confirm the lytic role of acid phosphatase.

The lysosomal enzyme N-acetyl-beta-glucosaminidase in rabbit muscle following a period of ischaemia

N-acetyl-beta-glucosaminidase activity increased in injured plantar muscle during the interval of 1 to 7 days after a period of 6 hours ischaemia of the rabbit hindpaw. Histochemical visualization demonstrated that this increased activity was not only associated with infiltrating inflammatory cells but also with the appearance of discrete lysosomal-like granules within damaged muscle fibres. Seven days after injury, the enzyme activity had reached a maximum with levels in the injured muscle 11 times higher than in normal muscle. The activity at this time was visualized in granules longitudinally arranged along regenerating muscle fibres, seemingly implicating the longitudinal sarcotubular system in their origin. Residual histochemical activity was evident at 14 and 28 days after injury. It is suggested that, in addition to its hydrolytic activity, N-acetyl-beta-glucosaminidase may have a role in the formation of mucopolysaccharides in the regenerative processes of muscle.