Reversible expression of sm α‐actin protein and sm α‐actin mRNA in cloned cerebral endothelial cells

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Abstract
The expression of smooth muscle (sm) α‐actin was studied in cloned capillary cerebral endothelial cells of two phenotypes. Type I cells were cultured in medium containing 10% FCS, heparin and ECGS (or α‐ECGF) and stained positive for a specific endothelial cell marker (Bandeiraea simplicifolia). Depletion of heparin and ECGS resulted in a smooth muscle‐like appearance after 2–3 days. Cells of this phenotype, (type II) stained positive for the endothelial cell marker and for sm α‐actin. In contrast to type I cells, type II cells expressed sm α‐actin protein and mRNA as evidenced by Immunoblots and Northern blots. This phenotypic switch was shown to be reversible and so was the expression of sm α‐actin.