Characteristic expression of GD1 alpha-ganglioside during lactation in murine mammary gland

Cellular proliferation and differentiation in mammary gland are known to be significantly altered during pregnancy and subsequent lactation. To characterize the different stages of mammary gland during pregnancy and lactation, we analyzed the glycosphingolipid compositions in the mammary gland of DDD and ICR mice at several periods of pregnancy and lactation, and found that the ganglioside composition, but not neutral glycosphingolipids, was characteristically altered during the pregnancy and lactation periods. The concentrations of acidic glycosphingolipids, I3SO3-GalCer 1, GM3, GM1a, GM1b and GD1a, were reduced during the course of pregnancy and lactation. GD1 alpha (III6NeuAc alpha,IV3NeuAc alpha-Gg4Cer) was first detected at the mid-period of pregnancy (12 days of pregnancy for ICR mice), increased in concentration at the late-period of pregnancy (GD1 alpha concentration was 100 times higher at 18 days than that at 12 days of pregnancy), and was a major ganglioside comprising 60-70% of the total lipid-bound sialic acid in the mammary gland of ICR and DDD mice at the lactation period, indicating that expression of GD1 alpha is associated with the lactating mammary gland of mice. In fact, GD1 alpha was highly concentrated in the milk fat globule, in which it was a major component.