2,3-Butanedione monoxime suppresses primarily total calcium handling in canine heart

Whether 2,3-butanedione monoxime (BDM, less than or equal to5 mmol/l) suppr esses primarily crossbridge cycling or total Ca2+ handling in the blood-per fused whole heart remains controversial. Although BDM seems to suppress pri marily total Ca2+ handling in canine hearts, more evidence is lacking. We t herefore analyzed the cardiac mechanoenergetics, namely, E-max (contractili ty), PVA (total mechanical energy), and O-2 consumption of canine BDM-treat ed hearts by our recently developed integrative method to assess myocardial total Ca2+ handling. This method additionally required the internal Ca2+ r ecirculation fraction. We obtained this from the beat constant of the expon ential decay component of the postextrasystolic potentiation. Our analysis indicated significant decreases in both internal Ca2+ recirculation fractio n and total Ca2+ handling in the BDM-treated heart, but virtually no change in the reactivity of E-max to total Ca2+ handling. This result corroborate s the view that BDM suppresses primarily total Ca2+ handling rather than cr ossbridge cycling in the canine blood-perfused heart.