Journal of Lipid Research, Vol 24, 533-540, Copyright © 1983 by Lipid Research, Inc.
Effects of human brain cell culture conditions on [14C]glucosamine radioactivity incorporation into gangliosides
VA Liepkalns, C Icard-Liepkalns, AJ Yates, S Mattison and RE Stephens
Human glioma cells (12-18) and fetal neural cells (CH II) in culture were
exposed for 20 hr to [14C]glucosamine to determine the level and
distribution of radiolabel incorporated into gangliosides. Cells of
identical passage levels at two stages of growth, preconfluent and
confluent, were preincubated for 0 to 60 hr in serum-free medium (SFM).
Both higher cell densities and longer incubations in SFM caused a change in
the amounts and patterns of radiolabeled gangliosides. Preincubation for 60
hr in SFM caused an increase (P less than 0.05) in the percent of total
recovered ganglioside radiolabel in GM1 of CH II cells, from 10.5 to 16.7%
in preconfluent cells and from 14.1 to 31.9% in confluent cells.
Conversely, the proportion of radiolabel in GM3 and GM2 decreased with
longer preincubations in SFM. A similar preincubation of glioma cells
caused an increase in the proportion of label into GD1a of both
preconfluent and confluent cells (P less than 0.02) from 4 to 11% of the
total ganglioside radioactivity. Higher cell densities also resulted in
consistently higher percent (of total ganglioside) incorporation into GD1a
of 12-18 cells (P less than 0.05) and GM1 of CH II (P less than 0.01).
These results show that there is a shift in the incorporation of precursor
label into more complex gangliosides under conditions associated with the
arrest of cell division. These phenomena may represent a regulatory
response of the ganglioside biosynthetic apparatus to changes in
extracellular environment and cell contact.
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