Sialyltransferase activities in cultured rat hepatocytes

Previous studies on the age and sex dependency of the ganglioside patterns in rat liver in vivo and the concomitant determination of the activities of some enzymes involved in these pathways revealed the prominent role of the sialylation of G M3 to G D3 in determining the flow to the mono (a)- and polysialo (b)-series, respectively. Here, the influence of hormones on the activities of G M3 and G D3 synthases in isolated hepatocytes was studied. The combination of several factors (insulin, glucagon, epidermal growth factor, glucocorticoids) was found to be necessary for maintaining in vivo activity levels of G D3- but not of G M3-synthase.