De novo synthesis and recycling pathways of sphingomyelin in rat sertoli cells

Sertoli cells from 19-day-old rats have two molecular species of sphingomye lin (SM1 and SM2) with different kinetic characteristics and fatty acid com position. Here, we have studied the incorporation of [C-14]choline and [C-1 4]-palmitic acid into SM in presence or absence of fumonisin B-1, an inhibi tor of ceramide synthesis, and beta -chloroalanine, an inhibitor of sphinga nine synthesis. The contributions of de novo synthesis and recycling pathwa ys were estimated by analysis of the inhibition caused by these drugs. SM1 was synthesized more by sphingosine recycling, and SM2 was synthesized prin cipally by ceramide recycling than SM1, De novo synthesis seems to be impor tant for the two SM types, but our results showed that this pathway is more extensively utilized by SM2. In conclusion, using Sertoli cell cultures, w e have shown for the first time that in the same cell different molecular s pecies of SM are synthesized by different pathways. (C) 2001 Academic Press .