Nucleotide depletion in hypoxia experimental models of mouse myocardial slices

Experimental models to test the effective protection against cardiac ischemia injury are still challenging in pre-clinical studies. The use of myocardial slices creates a special link between testing isolated cardiomyocytes and whole-heart research. In this work, we investigated the effects of oxygen deprivation in a hypoxic chamber and treatment with cobalt chloride (CoCl₂) on the nucleotide profile in isolated mouse myocardial slices.

200 μm-thick left ventricle myocardial slices were obtained from 3-month-old male C57Bl/6J mice using an oscillatory microtome. Slices were then exposed to 1% O₂ atmosphere or 100 μM CoCl₂ at 37 °C for 45 min and used for nucleotide measurements using ultra-high-performance liquid chromatography. The effects of two short-term experimental models of hypoxia were compared to 2'-deoxyglucose with oligomycin (2-DG + OLIGO) treatment, which inhibited both glycolysis and mitochondrial ATP synthesis.

A significant effect of hypoxia with 1% O₂ was observed on adenosine triphosphate (ATP) and total adenine nucleotide (TAN) concentrations as well as on adenylate energy charge (AEC), ATP/ADP and ATP/AMP ratios. Oxygen deprivation caused changes almost as profound as 2-DG + OLIGO, emphasizing the critical role of mitochondrial oxidative phosphorylation in the energy metabolism of cultured heart slices. CoCl₂ treatment that elicits hypoxia-like responses via HIF-1α stabilization only slightly affected nucleotide levels. This suggests that mechanisms induced by cobalt ions require more time to change the cardiac energy metabolism.

A short-term culture of myocardial slices in a hypoxic chamber seems to be an appropriate model of cardiac ischemia for testing new pharmacological approaches based on modulating the energy metabolism of cardiac cells.