SUMMARY1. Percutaneous needle biopsies were obtained from six limb muscles in six horses before and during a training programme of 10 or 15 weeks designed to involve both aerobic and anaerobic work. In a subsequent detraining period, biopsies were also taken after 5 and 10 weeks.2. Samples were analysed biochemically for enzyme activity of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aldolase (ALD), citrate synthase (CS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) and for glycogen content. Fibre typing was carried out histochemically before and 10 weeks after commencement of training.3. There was a significant increase in the percentage of high myosin ATPase activity pH 9.4/high oxidative (FTH) fibres with a corresponding decrease in high myosin ATPase activity pH 9-4/low oxidative (FT) fibres and low myosin ATPase activity pH 9-4/high oxidative (ST) fibres after 10 weeks training.4. During training, enzyme activities increased progressively but at different rates with an approximate twofold increase in all of the enzymes except CPK by the end of the training period. Changes in all the muscles studied were similar. Glycogen content inr-Qased by approximately 33 % which was significant when all the muscles ;ere considered together.5. A decrease in enzyme activity occur:.ei after 5 weeks detraining. However at 10 weeks a consistent but inexplicable increase in all enzyme levels, except CS again occurred.6. It is concluded that training increased greatly the activity of enzymes involved in both aerobic and anaerobic metabolism.
Acetyl-CoA carboxylase has been purified from lactating rat mammary gland using a combination of ammonium sulphate and poly(ethyleneglyco1) precipitations. The enzyme was purified from 35-70-fold with a yield of ovier SO%, the exact figures being difficult to estimate because of activation of the enzyme that occurs during the preparation. The preparation was homogeneous by the criterion of polyacrylamide gel electrophoresis in sodium dodecyl sulphate and had a single subunit of molecular weight 240000, containing 1.02 f 0.04 molecules of biotin and 3.1 +_ 1.7 molecules of alkali-labile phosphate per subunit. The purified enzyme was phosphorylated and inactivated rapidly when incubated in the presence of [Y-~'P]ATP and magnesium ions with the purified catalytic subunit of cyclic-AMP-dependent protein kinase from rabbit skeletal muscle. Both phosphorylation and inactivation are blocked by the heat-stable protein inhibitor of cyclic-AMP-dependent protein kinase, and can be reversed by incubation with purified protein phosphatase-1 from rabbit skeletal muscle. The inactivation by the protein kinase and reactivation by the protein phosphatase correlate with the near-stoichiometric phosphorylation and dephosphorylation of site(s) located in a single tryptic peptide. Phosphorylation does not affect the K,,, for substrates, but brings about a twofold decrease in V and a twofold increase in the apparent dissociation constant for the allosteric activator, citrate. We also present evidence that the activation of rabbit mammary acetyl-CoA carboxylase by protein phosphatase-1 described previously [Hardie and Cohen (1979) FEBS Lett. 103, 333-3381 is due to dephosphorylation at site(s) which are not phosphorylated by either cyclic-AMP-dependent protein kinase or acetyl-CoA carboxylase kinase-2.These results suggest that the rapid inactivation of acetyl-CoA carboxylase, and hence fatty acid synthesis, by adrenaline in adipose tissue, or glucagon in the liver, is due to phosphorylation of the enzyme by cyclic-AMP-dependent protein kinase.
SUMMARY
The use of the technique of percutaneous needle biopsy in obtaining skeletal muscle samples in the horse is described. The biochemical, ultrastructural and histochemical investigations that can be carried out on this biopsy specimen are outlined. Analyses performed on the specimen may be used to obtain information on racing potential and state of fitness. These studies on normal horses will provide information for future investigations into the structural and biochemical alterations in muscle disorders in the equine.
RÉSUMÉ
On décrit l'emploi chez le cheval d'une technique de biopsie des muscles de la vie de relation: cette technique utilise une aiguille et la voie transcutanée.
Des recherches biochimiques et histochimiques que l'on peut mener à bien en employant cette technique sont indiquées.
Les analyses faites sur les prélèvements peuvent donner des indications sur l'aptitude à la compétition et sur le degré de préparation à l'épreuve.
Ces études faites sur des chevaux normaux devraient apporter des informations utilisables pour de futures recherches sur les altérations musculaires structurales et biochimiques chez le cheval.
ZUSAMMENFASSUNG
Die Verwendung der perkutanen Nadelbiopsie‐Technik zur Gewinnung von Muskelstücken beim Pferd wird beschrieben. Die biochemischen, ultra‐strukturellen und histochemischen Untersuchungen, die an einem derartigen Biopsiestück vorgenommen werden können, werden angegeben. Derartige Analysen können Informationen liefern über die potentielle Rennleistung und den Fitness‐Zustand. Die Studien am normalen Pferd werden die Grundlage liefern für zukünftige Untersuchungen über die strukturellen und biochemischen Veränderungen bei Muskelkrankheiten des Pferdes.
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