Identification and quantitation of free ceramides in human platelets.

Free ceramides were isolated from human platelets. Their structures were unequivocally determined by gas-liquid chromatography-mass spectrometry of the trimethylsilyl ether derivatives. The major components were N-(palmitoyl) sphingosine, N-(stearoyl) sphingosine, N-(eicosanoyl) sphingosine, N-(docosanoyl) sphingosine, N-(tetracosanoyl) sphingosine, and N-(tetracosenoyl) sphingosine. Sphinganine-and sphingadienine-containing ceramides as well as ceramides containing other unsaturated acids were also present. The amount of ceramides was determined by quantitative gas-liquid chromatography, using radioactive ceramide as internal standard and synthetic crystalline ceramides for comparison of peak areas. The concentration of ceramides was found to be 1.31 micro g/10(9) platelets or 0.47 micro g/mg of platelet protein.