The effects of 2,3-butanedione monoxime on initial heat, tension, and aequorin light output of ferret papillary muscles.

At low concentrations (up to 5 mM) the compound 2,3-butanedione monoxime (BDM) was found to reduce twitch tension and initial heat production in isolated papillary muscles without significantly affecting the size of the intracellular Ca2+ transient measured with aequorin luminescence. Higher concentrations of BDM caused further inhibition of twitch tension and heat production with a fall in the size of the Ca2+ transient. The size of the aequorin transient was 50% of the control value at 15 mM BDM while twitch tension was negligible. These results suggest that BDM selectively inhibits Ca2+ activated force in cardiac muscle at low concentrations with additional effects on intra-cellular calcium at concentrations above 5 mM.