title: Effects of 2,3-butanedione monoxime on the crossbridge kinetics in frog single muscle fibres.
abstract: The effects of 2,3-butanedione monoxime (BDM) on contraction characteristics were studied at 5 degrees C in single intact fibres isolated from the tibialis anterior muscle of the frog. The force-velocity relation was determined using the controlled-velocity method in either whole fibres or short fibre segments in which sarcomere shortening was measured by a laser light diffraction method. It is shown that 3 mM BDM decreases the speed of rise and the amount of tetanus tension, reduces the maximum velocity of shortening and increases the curvature of the force-velocity relation, as well as the value for the stiffness to tension ratio. BDM also slowed down the redevelopment of tetanus tension after a period of unloaded shortening both in fixed-end and in length-clamp conditions. In normal and in BDM-treated fibres length-clamping increased the speed of the initial rise of tetanus tension but not that of the recovery after shortening. The observed force-velocity data points were fitted by the Huxley (1957) equation. It was found that BDM produces a conspicuous decrease of the rate constant for crossbridge attachment. This effect, and also a reduction of the force per crossbridge, are responsible for the depression of the contractile characteristics produced by BDM.
authors.affiliation: Dipartimento di Scienze Fisiologiche, Università di Firenze, Italy.
authors.forename: M A
authors.initials: MA
authors.lastname: Bagni
authors.forename: G
authors.initials: G
authors.lastname: Cecchi
authors.forename: F
authors.initials: F
authors.lastname: Colomo
authors.forename: P
authors.initials: P
authors.lastname: Garzella
mesh_terms: D000205:Actomyosin / Q000187:drug effects*; D000818:Animals; D001696:Biomechanical Phenomena; D003931:Diacetyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects*; D011893:Rana esculenta
chemical_list: C004717:diacetylmonoxime; D000205:Actomyosin; D003931:Diacetyl