Distribution and particle properties of acid hydroase in denervated muscle

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Abstract
Cathepsin D, aryl sulfatase, acid RNase, [beta]-glucuronidase, and acid phosphatase were studied in rat lower leg muscles during the 1st week of denervation atrophy and in contralateral muscles having intact innervation. The distribution of enzyme activity after differential and isopycnic gradient centrifugation and the properties of enzyme associated with small sedimenting particles were investigated. The particles behaved in centrifugal fields like the lysosomes of liver with the exception that they did not appear to take up intravenously injected Triton WR-1339. The particulate enzymes exhibited latent activity and in vitro release of free and unsedimentable activity after osmotic stress. Increases in the proportion, specific activity, and in vitro release of unsedimentable enzyme after denervation suggest an increased fragility of the particles. Increases in total specific activity seemed to involve new enzyme synthesis or differential sparing of enzyme from increased breakdown rather than change in optimum conditions of assay, inhibitor activity, autolytic activity, or macrophage invasion.