FIGURE 9. Cardiolipin content of iPLA₂γ knock-out mouse myocardium.

Mouse heart tissues were obtained from 3–4-month-old wild type (WT) or iPLA₂γ KO (KO) mice fed ad libitum. Mouse myocardial lipids were extracted by a modified Bligh and Dyer method and subjected to electrospray ionization/mass spectrometry analyses in the negative ion mode as described under “Experimental Procedures.” The levels of individual cardiolipin molecular species after identification were calculated in comparison with the selected internal standard after ¹³C deisotoping as described previously (26). A, alterations in total cardiolipin content (nmol of CL/mg of protein) between WT and iPLA₂γ KO mice. B, alterations in the content of the major cardiolipin species, tetra-18:2 CL (nmol/mg protein) in iPLA₂γ KO versus WT mice. Experiments were performed with three WT and five KO animals between 3 and 6 months in age. Significant decreases in both total cardiolipin (p < 0.005) and tetra-18:2 CL species (p < 0.02) were consistently observed in iPLA₂γ KO hearts.