Synthesis of Galactosylceramide and Glucosylceramide by Mouse Kidney Preparations

A particulate fraction was prepared from kidneys, lyophilized, and coated with ceramide. After incubation with UDP-[14C]Gal and appropriate cofactors, the major radioactive component in the lipid fraction was galactosylceramide (Gal-Cer). If UDP-Glc was substituted for UDP-Gal, the product was glucosylceramide (Glc-Cer). Specific activity for Gal-Cer synthesis was present at comparable levels in kidney preparations from males or females at early ages. However, between 20 and 30 days of age there was a 5-fold increase in activity in preparations from male kidney, followed by a slight decline. In contrast, Gal-Cer synthesis in kidney preparations from female mice decreased slowly from 10 to 70 days of age. Despite the low levels of Gal-Cer in kidney, enzymatic activity for its synthesis was high, 0.8 nmole per mg of protein per hour in 30-day-old males. This was 40% of the specific activity for Gal-Cer synthesis in brains of the same animals. Glc-Cer synthesis by kidney followed a developmental pattern markedly different from that for Gal-Cer formation. There was an increase in activity throughout the time period studied (10 to 64 days of age), but activity was most rapid between 30 and 40 days of age. Activity in preparations of female kidney followed a similar pattern but was lower than that of preparations from males at 10 days of age and increased less rapidly. In kidneys of mature male animals, the specific activity for Glc-Cer synthesis was twice that of the females.