GANGLIOSIDE-MEDIATED METABOLIC SYNCHRONIZATION OF PROTEIN SYNTHESIS ACTIVITY IN CULTURED HEPATOCYTES

An ultradian oscillation of protein synthesis was detected by synchronization of metabolic activity in rat hepatocyte cultures. This oscillation occurs in dense cultures in fresh medium, but not in sparse ones. Metabolic synchronization of sparse cultures, however, was initiated by conditioned medium or addition of 0.3–0.5μm of a mixture of bovine brain gangliosides to fresh culture medium along with either 0.06–0.2μm GM1 or 0.1–0.2μm GDIa. GTIb and GDIb did not produce oscillations, nor did human liver ganglioside GM3. High expression of GM1 ganglioside determinants in hepatocytes maintained in the conditioned medium purified polyclonal antibodies to GM1 was coupled with protein synthetic oscillatory activity, i.e. metabolic synchronization. Incubation of dense cultures with GM1-antibodies for 24h decreased the amplitude of these oscillations. In sparse cultures maintained in fresh medium where protein synthesis showed no oscillatory pattern, GM1 expression was low.