BDM compared with P(i) and low Ca2+ in the cross-bridge reaction initiated by flash photolysis of caged ATP.
Using flash photolysis of caged ATP in skinned muscle fibers from rat psoas, we examined the inhibitory effects of 2,3-butanedione monoxime (BDM) on the contraction kinetics and the rate of ATP hydrolysis of the cross-bridges at approximately 10 degrees C. The hydrolysis rate was estimated from the stiffness records. The effects of BDM were compared with those of orthophosphate (P(i)) and of reduction in [Ca2+] (low Ca2+), and it was found that i) BDM and low Ca2+ inhibited ATPase activity to the same extent as they inhibited the steady tension, whereas P(i) inhibited ATPase activity much less than tension; ii) BDM and P(i) decreased tension per stiffness during the steady contraction more than did low Ca2+; iii) neither BDM nor low Ca2+ affected the initial relaxation of the fiber on release of ATP, but P(i) slightly slowed it; and iv) BDM hardly influenced the rate of contraction development after relaxation, although P(i) and low Ca2+ accelerated it. We concluded that BDM inhibits the Ca(2+)-regulated attachment of the cross-bridges and force-generation of the attached cross-bridges.
Kagawa
K
K
Department of Physiology, Oita Medical University, Japan.
Horiuti
K
K
Yamada
K
K
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002863:Chromogenic Compounds / Q000494:pharmacology; D003931:Diacetyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D010710:Phosphates / Q000494:pharmacology*; D010782:Photolysis; D051381:Rats; D012518:Sarcomeres / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D002863:Chromogenic Compounds; D010710:Phosphates; C004717:diacetylmonoxime; C029273:P(3)-1-(2-nitro)phenylethyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D003931:Diacetyl; D002118:Calcium