Sphingolipids of transplantable rat Nephroma-RA

Contents of sphingolipids (ceramide, sphingomyelin, gangliosides) and the c omposition of their sphingoid bases were studied in the transplantable rat nephroma-RA and in rat kidneys. The content of sphingomyelin was about 1.3- fold decreased and the content of ceramide was about 1.4-fold increased in the nephroma compared to normal kidneys, and this correlated with a 1.4-fol d increased activity of neutral sphingomyelinase; however, the activity of the acidic isoform of the enzyme was virtually unchanged. The content of ga ngliosides was also increased in the nephroma. Ceramide and sphingomyelin o f the nephroma, in addition to sphingosine, contained a significant amount of sphinganine, although a considerable amount of the latter was also found in the renal ceramide. The ratio sphingosine/sphinganine in sphingomyelins changed from 65:1 in kidneys to 5:1 in the nephroma. Thus, the biosynthesi s of sphingoid bases seems to be disturbed in the transplantable rat nephro ma-RA compared to normal kidneys.