Figure 4.

Quantification of High-Energy Phosphate Content of Perfused Hearts Throughout the Experimental Protocol

Pseudoquantification of the [ATP] and [PCr] was performed by assuming that the [ATP] in baseline healthy hearts was 10.6 mmol/l in the fully relaxed 10-min acquisition. All spectra were referenced to this initial spectrum. Each parameter was measured from the spectra acquired over the final 5 min of the baseline period, of ischemia, and of reperfusion, respectively. (A) When averaged across the group of hearts, PCr was significantly reduced during ischemia and recovered after 45 min of reperfusion. (B) ATP was maintained throughout the ischemic period, but was depleted after 45 min of reperfusion. (C) Regression analysis revealed that [ATP] has a segmental relationship with ¹³C-malate production (expressed as malate/fumarate relative to the equivalent baseline value). When [ATP] was maintained above 5.3 mmol/l, very low levels of ¹³C-malate production were observed. Below this [ATP] threshold, each unit of [ATP] depletion (in mmol/l) resulted in a 74% increase in ¹³C-malate production. ∗p < 0.05 compared with healthy group. ATP = adenosine triphosphate; PCr = phosphocreatine.