Effects of Colchicine and Cytochalasin B on Labelling and Enzyme Activities of Brain Plasma Membranes

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Abstract
The possible involvement of colchicine-sensitive microtubules and cytochalasin B-sensitive microfilaments in. the transport of proteins into plasma membranes was studied in isolated cells from newborn rat brain and in vivo. Microtubules were detected in purified plasma membrane fractions. Colchicine inhibited 24 % of the labelling of plasma membrane proteins during a 4-hour incubation of the cells and 35 % during one day labelling in vivo. Cytochalasin B had no effect. The two drugs depressed the specific activity of acetylcholinesterase and choline acetyltransferase in plasma membranes. These data suggest that colchicine interfered with the transport of some proteins in brain plasma membranes. The inhibition of enzyme activities in plasma membranes by the two drugs may indicate a rearrangement of membrane proteins.