title: Function dependent changes in the subcellular distribution of high energy phosphates in fast and slow rat skeletal muscles.
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 [sigma(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 approximately 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.
mesh_terms: D000244:Adenosine Diphosphate / Q000032:analysis / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D004558:Electric Stimulation; D007551:Isotonic Contraction; D008297:Male; D009132:Muscles / Q000032:analysis / Q000502:physiology*; D010710:Phosphates / Q000032:analysis*; D010725:Phosphocreatine / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010710:Phosphates; D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate