EVALUATION OF THE EFFICIENCY OF AN ASSAY PROCEDURE FOR GANGLIOSIDES IN HUMAN SERUM

An efficiency assessment of a ganglioside assay procedure was carried out on human serum gangliosides from healthy subjects of different sex and age. The analysis of the gangliosides, extracted with chloroform/ methanol and purified by lipid partitioning, ion exchange column chrom atographic separation and desalting procedures as described by Senn et al. (1989) Eur J Biochem 181: 657-62, was performed by HPTLC followed by densitometric quantification. The yield of the procedure, expresse d as radioactivity recovery, was determined by adding GM3 ganglioside, tritium labelled at the sialic acid acetyl group and at the C3 positi on of sphingosine, to the lyophilized serum or by associating it with the serum lipoproteins. Tn spite of the fact that the extraction and p urification procedures were performed exactly as described we found th e radioactivity recovery to be variable (25-50%) and much lower than t hat proposed. Much of the radioactivity was found in the organic phase after lipid partitioning, whilst all the ganglioside purification ste ps led to some further loss. After the introduction of some modificati ons to the procedure the recovery improved, reaching 67-79%. The analy ses on 33 samples of 5 ml showed a human serum ganglioside content of about 10 nmol ml(-1) (as corrected for the recovery), and confined tha t GM3 ganglioside is the main component of the total serum ganglioside mixture.