Immunochemical determination and immunocytological localization of brain-specific protein alpha-albumin (GFA) in isolated astrocytes.

Astrocyte- and neuron-enriched fractions were isolated by preparative centrifugatin from rat brain and human brain, obtained at autopsy. The brain-specific protein alpha-albumin (GFA) was studied in these fractions by quantitative immunoradiochemical and by immunocytological methods. It is concluded that morphologically intact astrocytes can be isolated not only from rat, but also from human brain. In the rat, alpha-albumin (GFA) is only found in the astrocyte-enriched fractions; this shows that detemination of alpha-albumin (GFA) is useful for the evaluation of cell separation methods for the brain. From the astrocyte-enriched fractions, four times more alpha-albumin (GFA) can be extracted when detergent (0.1% SDS) is used, than when an aqueous extract is made. About +/- 0.15 X 10(-6) particles were extracted in 1 ml of either PBS or SDS/PBS. This suggests that alpha-albumin (GFA) exists in at least two forms, one hydrosoluble, and one detergent soluble, possibly structurally bound, form.