Contractile activation and the effects of 2,3-butanedione monoxime (BDM) in skinned cardiac preparations from normal and dystrophic mice (129/ReJ)

Abstract

Small cardiac myofibrillar preparations were obtained from the right ventricle of normal (129/ReJ) and dystrophic (129/ReJ dy/dy) mice and were chemically skinned in a relaxing solution by exposure to Triton X-100 (3% v/v). (2) The isometric force produced in these skinned cardiac preparations at different sarcomere lengths was measured in solutions of different [Ca2+] and ionic strength. The effect of the negative inotropic drug 2,3-butanedione monoxime (BDM), which is known to act at the myofibrillar level was also investigated. (3) The murine cardiac preparation from normal animals was found to develop 50% maximal force at a pCa (= -log10[Ca2+]) of 5.59 +/- 0.08 and 5.94 +/- 0.03 (mean +/- SD) under physiological (ionic equivalents concentration, I = 154 mM; pH 7.10; [Mg2+] 1 mM) and low ionic strength (I = 94 mM; pH 7.10; [Mg2+] 1 mM) conditions respectively. The isometric force curves were significantly shallower at low ionic strength (Hill coefficient, 1.8 +/- 0.1) than at physiological ionic strength (Hill coefficient, 2.6 +/- 0.3) and the sarcomere length effect on the force-pCa relation was markedly reduced at lower ionic strength. (4) Increasing BDM concentrations in solutions up to 100 mM reduced the maximum Ca2+-activated force of cardiac preparations from normal mice to less than 6% of the control values in a dose dependent fashion. BDM also rendered the cardiac preparations less sensitive to Ca2+ by a factor of up to 1.5 in a process which showed saturation at BDM concentrations higher than 15 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Optical Action Potential Screening on Adult Ventricular Myocytes as an Alternative QT-screen

“…1C) did not "ratio out" entirely. Consequently, we suppressed contraction by 20 mM BDM, a compound well known for suppressing contractile responses in cardiac muscle [26]. In addition we found that in cardiomyocytes upon depolarisation at room temperature, Mermaid fluorescence did not display any change, despite contractile responses (data not shown).…”

Altered myocardial force-frequency relation in human heart failure.

“…25 In rat cardiomyocytes, exposure to 20-mmol/l BDM and washout was without effect on contractility,26'27 membrane outward currents,28 energy metabolism, and ultrastructure.27 Even with exposure to much higher doses of BDM (50 and 100 mmol/l) in which, in the presence of the drug, a differential effect on contractility of normal compared with dystrophic mouse myofibrils was observed, the BDM effects were completely reversible. 29 The absence of an irreversible effect on these aspects of contractile function in myocardial cells of other mammalian species suggests that BDM effects are similarly reversible in human myocardium. Additionally, evidence that even prolonged soaking in 30-mmol/l BDM solution does not cause irreversible effects comes from the present control experiments showing that the twitch and the tension-frequency curves of human myocardium are not different with 1 hour compared with 10 hours of soaking.…”

Contractile activation and measurements of intracellular Ca2+ concentration in cane toad twitch fibres in the presence of 2,3‐butanedione monoxime

“…2,3-Butanedione monoxime (BDM), or diacetyl monoxime, is a drug with phosphatase-like activity, which has been shown to inhibit contractility in both cardiac (Wiggins, Reiser, Fitzpatrick & Bergey, 1980;West & Stephenson, 1989;Backx, Gao, Azan-Backx & Marban, 1994) and skeletal muscle Neering & Stephenson, 1988 b; McKillop, Fortune, Ranatunga & Geeves, 1994).…”

“…The inhibitory effects of BDM on force development in cardiac muscle are largely due to a direct effect of BDM on the contractile apparatus (Li, Sperelakis, Teneick & Solaro, 1985;West & Stephenson, 1989) where it inhibits cross-bridge cycling (Blanchard, Mulieri & Alpert, 1984;Blanchard, Alpert, Allen & Smith, 1988;Backx et al 1994). Measurement of heat production and intracellular [Ca2+] with aequorin (Blanchard et al 1988) and fura-2 (Backx et al 1994) during contraction of cardiac muscle showed BDM to have a relatively minor effect on the [Ca2+] changes associated with activation.…”