Comparing phospholipid profiles of mitochondria and whole tissue: Higher PUFA content in mitochondria is driven by increased phosphatidylcholine unsaturation.

Phospholipids content in cellular and mitochondrial membranes is essential for maintaining normal function. Previous studies have found a lower polyunsaturated fatty acid (PUFA) content in mitochondria than whole tissue, theorizing decreased PUFA protects against oxidative injury. However, phospholipids (PPLs) are uniquely difficult to quantify without class separation and, as prior approaches have predominately used reverse-phase HPLC or shotgun analysis, quantitation of PPL classes may have been complicated due to the existence of numerous isobaric and isomeric species. We apply normal-phase HPLC with class separation to compare whole tissue and mitochondrial PPL profiles in rat brain, heart, kidney, and liver. In addition, we establish a novel method to ascertain PPL origin, using cardiolipin as a comparator to establish relative cardiolipin /PPL ratios. We report a higher PUFA content in tissue mitochondria driven by increased phosphatidylcholine unsaturation, suggesting mitochondria purposefully incorporate higher PUFA PPLs.