Über die Bindung der Muskelaldolase an grobdisperse Partikeln in Homogenaten erregter Muskeln

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Abstract
Groups of muscles in rats anesthesized with urethane were stimulated for 10-70 sec. with an electronic stim-ultor (10 mA, duration of impulses 1 msec, frequency 50 impulses/ minute), and removed at intervals between 0 and 29 min. after termination of the stimulation. The muscles were homogenized with an Ultra Turrax, centrifuged at low speed, and the activity of several enzymes was determined in the supernatant by optical methods. The enzymes investigated were aldolase, creatine kinase, aspartate trans-aminase, lactic dehydrogenase, malate dehydrogenase, adenylate kinase, triosephosphate isomerase. Among these aldolase showed a peculiar behavior; its activity was strongly decreased after stimulation, basing the specific activities either on wet weight, or mg protein in the supernatant. If the muscle is removed immediately after termination of the stimulation and homogenized either in bidistilled water or in 0.25[image] sucrose, the activity found is only 20% of the activity in extracts prepared from resting muscle under identical conditions. If the muscle is left in situ after the stimulation, and is removed at intervals only, the activity found in the extracts first rises quickly, then more slowly and levels off at 80% of the activity found in resting muscle after 30 min. The activity missing from the supernatant from stimulated muscle can be recovered from the sediment of the low speed centrifugation by treatment with electrolyte solutions. If the muscle is either extracted with electrolyte solutions, or if the extract is made with sucrose solution, and electrolyte is added before centrifugation, the activity of aldolase found in the supernatant from stimulated muscles nearly equals that found in the supernatant from resting muscles. This activity is higher than the activity which can be extracted from resting muscle by sucrose only. If electrolyte is added after centrifugation, no increase of the activity is observed. Treatment with detergents or with ultrasound is much less effective than extraction with electrolytes. Aldolase can be bound to membranes and/or nuclei, and that the amount bound increases several times by prior stimulation of the muscles.

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