GLYCOSPHINGOLIPID COMPOSITION OF RAT PLACENTA - CHANGES ASSOCIATED WITH STAGE OF PREGNANCY

The composition of glycolipids and their changes in the placenta were investigated in the normal pregnant rat. Total lipid fractions extract ed from the placenta between days 12 and 20 of pregnancy (day 0 = oest rus) were subjected to glycolipid analysis using DEAE-Sephadex chromat ography, silica-gel HPLC, silica-gel TLC, TLC/immunostaining, matrix-a ssisted secondary-ion mass spectrometry in the negative-ion mode and H -1 NMR. Glycolipids identified in the rat placenta were: gangliosides G(M3) (NeuAcLacCer and NeuGcLacCer) and G(D3) (NeuAcNeuAcLacCer, NeuAc NeuGcLacCer and NeuGcNeuAcLacCer), and neutral glycolipids ceramide mo nosaccharide (CMH) (GlcCer), ceramide disaccharide (CDH) (LacCer), cer amide trisaccharide(CTH) (Gb(3)Cer) and ceramide tetrasaccharide (CQH) (Gb(4)Cer). The content of neutral glycolipids was higher than that o f gangliosides throughout pregnancy. Of the neutral glycolipids, CMH a nd CTH predominated and the level of CDH was low at mid-pregnancy. Dur ing late pregnancy, CMH and CTH decreased and CDH increased markedly. CQH remained at a low level throughout pregnancy. Of the gangliosides, G(M3) was predominant on days 12-16 and then decreased, whereas GD(3) , which was low on day 12, increased slightly on day 16 and maintained the same level thereafter. Immunohistochemical studies indicated that these changes in the expression of major gangliosides from G(M3) to G (D3) occurred in labyrinthine trophoblasts. Thus expression of these g lycolipids appears to change markedly during pregnancy.