Cerebroside and sulfatide biosynthesis in the brain of Snell dwarf mouse: effects of thyroxine and growth hormone in the early postnatal period.

Snell dwarf mice (dw/dw) and normal mice (+/?) were injected with thyroxine (T4) (1 microgram/animal, four injections) and growth hormone (GH) (20 micrograms/animal, four injections) from the 5th to the 15th day of life. In the untreated dw/dw mouse brain, the specific activities of UDP-galactose:ceramide galactosyltransferase (CGalT), PAPS:cerebroside sulfotransferase (CST), and 2', 3'-cyclic nucleotide 3'-phosphohydrolase (CNP) were decreased by 28, 25, and 37%, respectively, compared with the control untreated +/? mice. The major effect of T4 was an increase of the brain CNP in the +/? mice (+40%) and dw/dw mice (+111%). The treatment with T4 also brought to normal the level of CGalT in dw/dw brain; a somewhat less marked effect on CST was observed. The treatment with GH had a great stimulatory effect on CNP: the specific activity of this enzyme increased by 40 and 69% in +/? and dw/dw mouse brain, respectively. On the contrary, no effect of GH on the CGalT activity was observed in this study. Our results suggest that T4 and GH may have both independent and complementary actions on the myelin-associated enzymes during the early postnatal period of brain development.