THE ROLE OF CYCLIC AMP-MEDIATED REGULATION OF GLYCOGEN-METABOLISM IN LEVAMISOLE-PERFUSED ASCARIS-SUUM MUSCLE

  • 1 January 1983
    • journal article
    • research article
    • Vol. 23  (2) , 378-383
Abstract
The effects of levamisole on muscle contraction and glycogen metabolism were examined in isolated muscle-cuticle sections of the roundworm A. suum. Muscle contraction occurred when various levels of levamisole were perfused through the preparation. At a levamisole concentration of 0.42 mM, the period of contraction lasted only .apprx. 6 min and was followed by a period of relaxation. During this relaxation period, there was an activation of glycogen synthase (EC 2.4.1.11), as evidenced by a decrease in the K.alpha. values of G-6-P for glycogen synthase to 0.26 mM for control values of 0.50 mM. The glycogen phosphorylase (EC 2.4.1.1) activity ratio decreased from 0.85 to 0.65, which indicated an inactivation of this enzyme. Concomitant with this activation of glycogen synthase and inactivation of phosphorylase there was an increased synthesis of glycogen. The presence of levamisole prevented both the serotonin-induced cAMP accumulation and the activation of the cAMP-dependent protein kinase (EC 2.7.1.37). Levamisole did not significantly affect the changes in glycogen synthase and phosphorylase brought about by perfusion with the neurostimulator acetylcholine. Levamisole seemed to caused a transient muscle contraction followed by muscle relaxation; the muscle relaxation effect appeared to be the result of a levamisole-inhibited cAMP-mediated pathway of glycogen utilization.

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