Heparin inhibits the growth of astrocytes in vitro.

Heparin at a concentration of 100 micrograms/ml, inhibits neonatal rat astrocyte proliferation by 45%, and [3H]thymidine incorporation into DNA by 55% when they are stimulated with 2% fetal bovine serum (FBS) in culture. Higher serum concentrations up to 10% FBS decreased this inhibition to 20% and 29% respectively. Inhibition of [3H]thymidine incorporation by heparin is dose-dependent with maximal inhibition at 100 micrograms/ml, but 39% inhibition is still seen at 1 microgram/ml on stimulation by 5% FBS. Heparin or heparin-like molecules in the extracellular matrix of brain capillary walls may be important in the regulation of astrocyte growth in vivo.