Function dependent changes in the subcellular distribution of high energy phosphates in fast and slow rat skeletal muscles |
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Authors: | S. Hebisch H. Sies S. Soboll |
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Affiliation: | (1) Institut für Physiologische Chemie I der Universität Düsseldort, Moorenstraße 5, D-4000 Düsseldorf 1, Germany |
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Abstract: | Function dependent changes in the subcellular distribution of ATP, ADP, creatine phosphate (CrP) and creatine (Cr) in rat fast-twitch gastrocnemius and slow-twitch soleus muscles were studied by fractionation of freeze-clamped and freeze-dried tissue in non-aqueous solvents.During 5 min of isotonic contraction of gastrocnemius muscles the mitochondrial content of total creatine [(CrP+Cr)] decreases by 9.5 nmol/mg total protein whereas there is an increase in extramitochondrial total creatine by 12.3 nmol/mg total protein, indicating a net transfer of 10 nmol total creatine/mg total protein/5 min across the mitochondrial inner membrane.During short-term stimulation (6 s) of gastrocnemius muscles the socalled additionally-bound ADP correlates not only with force (Hebisch et al. 1984) but also with filament overlap. This confirms the previous suggestion that additionally-bound ADP represents actomyosin-ADP-complexes.Following long-term stimulation (10 s), the rate of decay of force is at least two orders of magnitude faster than that of additionally bound ADP. This indicates a decrease of actomyosin-ADP complexes due to formation of myosin-ADP complexes.Short-term stimulation (6 s) of slow-twitch soleus muscles does not lead to any force-dependent change in the content of additionally-bound ADP, similar to the finding in long-term contracting gastrocnemius muscles. Denervation of soleus muscles leads to a decrease in additionally-bound ADP to values comparable to those found in resting fast-twitch gastrocnemius muscles. |
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Keywords: | Adenine nucleotide compartmentation ADP binding High-energy phosphate Muscle contraction |
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