FATTY-ACID DESATURASE ACTIVITIES AND POLYUNSATURATED FATTY-ACID COMPOSITION IN HUMAN LIVER BETWEEN THE 17TH AND 36TH GESTATIONAL WEEKS

OBJECTIVE: The aim of the study was to characterize n-3 and n-6 fatty acid Delta 5- and Delta 6-desaturase activities and their time course variations in human fetal liver between the 17th and 36th gestational week. STUDY DESIGN: Twenty-one biologic samples were obtained after le gally approved medical abortion, according to French law. The desatura se activities were measured in the 21 liver samples by a radiochemical method by means of reverse-phase high-performance liquid chromatograp hy. The fatty acid composition (percentage by weight) of liver phospho lipids was assessed in 16 samples by gas-liquid chromatographic analys is. RESULTS: Both Delta 5- and Delta 6-desaturase activities were sign ificantly expressed between the 17th and 36th gestational weeks. Durin g the second trimester n-6 fatty acid Delta 5- and Delta 6-desaturase activities showed opposite patterns of variation; both then remained s table between the 25th and 36th weeks. Delta 6-Desaturation was higher in n-3 than n-6 fatty acids and peaked at the 18th gestational week. The percentages of linoleic and docosahexaenoic acids in liver microso mes were positively correlated with the gestation age (P<.01), whereas arachidonic acid remained stable. CONCLUSION: Significant n-3 and n-6 Delta 5- and Delta 6-desaturase activities are expressed in human fet al liver as early as the 17th gestational week and are stable througho ut the third trimester. Their theoretic capacity evaluated from in vit ro measurements appears lower than polyunsaturated fatty acid requirem ents and is not directly related to liver microsomal membrane fatty ac id composition.