Effects of vanadate, phosphate and 2,3-butanedione monoxime (BDM) on skinned molluscan catch muscle.
The effects of orthovanadate (V(i)), inorganic phosphate (P(i)) and 2,3-butanedione monoxime (BDM) on tension, force transients and the catch state (passive tension maintenance) were investigated in saponin-skinned fibre bundles of the anterior byssus retractor muscle (ABRM) of the bivalve mollusc Mytilus edulis at pH 6.7. During maximal Ca(2+) activation isometric force was depressed by V(i) (0.03-10 mM), P(i) (10 mM) and BDM (50 mM). Force transients following quick stretches (0.1-0.3% of fibre length) were accelerated substantially by 1 mM V(i), 10 mM P(i) or 50 mM BDM. These compounds also accelerated force responses in experiments in which ATP was released rapidly from caged ATP by flash photolysis at both pCa 4.7 (force rise) and at pCa>8 (force decline). The effects on the catch state were investigated in two types of experiments: (1) Ca(2+) removal after maximal Ca(2+) activation and (2) rapid ATP release during high-force rigor at pCa>8. In both cases rapid relaxation was followed by slow relaxation (slower than 2% of initial force per min). This later slow relaxation (catch) was insensitive to V(i) (1-10 mM), P(i) (10 mM) and BDM (50 mM) but was accelerated by 0.12 mM cAMP. Complete relaxation to almost zero force was attained by changing pH from 6.7 to 7.7 (pCa>8). We conclude that catch depends on cAMP- and pH-sensitive structures linking the myofilaments and not on the force-generating actomyosin cross-bridges that are sensitive to V(i), P(i) and BDM.
Galler
Stefan
S
Department of Cell Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria. Stefan.Galler@sbg.ac.at
Höpflinger
Marion Christine
MC
Andruchov
Oleg
O
Andruchova
Olena
O
Grassberger
Herbert
H
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D049872:Bivalvia / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D003931:Diacetyl / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008465:Mechanoreceptors / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology; D009132:Muscles / Q000502:physiology*; D010710:Phosphates / Q000494:pharmacology*; D014638:Vanadates / Q000494:pharmacology*
D010710:Phosphates; C004717:diacetylmonoxime; D014638:Vanadates; D000255:Adenosine Triphosphate; D003931:Diacetyl