Impact of bicarbonate on ionized calcium and cardiac function in albumin‐free Langendorff perfusion in hearts of male rats

Abstract

The adult Langendorff methodology lacks standardization, with inconsistencies in the pH and calcium concentrations of Krebs–Henseleit (K‐H) solution. The aim of this study was to clarify these inconsistencies. Adult male Wistar rat hearts were subjected to 40 or 80 min of global ischemia followed by reperfusion. Recovery of left ventricular developed pressure (LVDP) and triphenyltetrazolium (TTC) staining were evaluated. Ion analysis was performed using rat plasma. A calcium concentration of 1.75 mM was associated with increased contractile force and more severe ischemia–reperfusion injury. The absence of preload resulted in increased variability in the results. LVDP recoveries were high and decreased with longer lengths of ischemia. Rat plasma exhibited higher total calcium and lower albumin levels than humans. The K‐H solution forms substantial amount of calcium complexes with bicarbonate, likely due to hypoalbuminemia, which also explains its alkaline nature. Rat plasma calcium activity closely corresponded to the K‐H solution with 1.75 mM Ca ²⁺ . These findings indicate that Langendorff perfusion experiments benefit from higher calcium and lower bicarbonate concentrations. Caution is warranted when preparing artificial solutions lacking albumin, as physiological ion concentrations may not correspond to physiological ion activities. Use of preload and longer lengths of ischemia may further improve experimental consistency.