AJP - Cell Physiology, Vol 249, Issue 5 484-C489, Copyright © 1985 by American Physiological Society
Insulin stimulates macromolecular synthesis in cultured glial cells from rat brain
D. W. Clarke, F. T. Boyd Jr, M. S. Kappy and M. K. Raizada
The effect of insulin on macromolecular synthesis in glial cells cultured
from brains of 1-day-old rats was studied to investigate the role of
insulin in brain growth. Insulin caused a dose-dependent stimulation of
protein synthesis (measured by [3H]valine incorporation into protein) that
became significant by 7 nM insulin. Maximal stimulation of protein
synthesis of 145% of control occurred with 18 nM insulin. Long-term protein
synthesis was also stimulated to 136% of control by insulin in a
dose-dependent manner after 6 days of insulin incubation. Insulin also
stimulated net RNA and DNA synthesis (measured by [3H]uridine and
[3H]thymidine incorporation into RNA or DNA, respectively) with significant
stimulation by 2 nM insulin. Net RNA synthesis stimulation was maximal at
120% of control by 18 nM insulin. Plateau stimulation of DNA synthesis of
175% of control was reached by 200 nM insulin. The effects of insulin on
glial protein and RNA synthesis appear to be mediated completely by the
insulin receptor. Insulin, in physiological concentrations, stimulated
glial DNA synthesis via its interaction with the insulin receptor (46% of
total response). At supraphysiological concentrations insulin may have
stimulated DNA synthesis via its cross-reactivity with the insulinlike
growth factor I receptor (54% of total response). Thus insulin, at
concentrations known to exist in the brain, stimulates the processes
necessary for growth in the glial cell and is an important growth factor in
the developing rat brain.
