2,3-Butanedione monoxime (BDM) exerts a marked negative inotropic effect and has been shown to have protective actions on human myocardial force production that may be of clinical use. To determine the underlying mechanisms, we studied the effects of BDM on chemically skinned and aequorin- loaded myopathic human myocardium from transplant recipients. Eighteen muscles were chemically skinned with saponin (250 μg/ml) and then subjected to activation-relaxation cycles, with and without 5 mM BDM. Contracture force vs. Ca2+ data were fitted to a modified Hill equation, and values for 50% maximal activation (pCa50) and maximal Ca2+-activated force (F(max)) were obtained. pCa50 was decreased by 0.2 pCa units, indicating myofilament Ca2+ desensitization, and F(max) was reduced by 48% in 5 mM BDM. A second group of intact muscles (n = 8) was loaded with aequorin to monitor intracellular calcium (Ca(i)/2+) transients (peak light) and twitch force in the presence of BDM (1-30 mM). Over a range of 1-20 mM, BDM depressed peak light by 3-49% while force was depressed by 10-82%. This was accompanied by an abbreviation of the duration of the twitch but not of the Ca(i)/2+ transient. At a concentration of 30 mM, BDM completely inhibited force generation, but an Ca(i)/2+ transient was still present. We conclude that in human myocardium, 5 mM BDM predominantly affects cross-bridge force production and Ca2+ sensitivity and has a less pronounced effect on Ca(i)/2+.
|Original language||English (US)|
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|Issue number||2 32-2|
|State||Published - 1992|
- calcium activation
- intracellular calcium
ASJC Scopus subject areas