Adenosine modifies colchicine-uptake into tissues from the mammalian brain

Colchicine is taken up by isolated cerebral tissues incubated in glucose-salt solutions and is maintained in the tissues when they are superfused with colchicine-free solutions. Most of the colchicine in such tissues remains uncombined after an hour's incubation; up to 20% is combined with tubulin of cytosolic and particulate fractions. Adenosine, and conditions of stimulation or depolarization which release adenosine, diminish the uptake of colchicine and less appears in combined forms. Uptake is diminished also by 2-chloroadenosine and by cyclic AMP; is increased by theophylline and by adenosine deaminase but unaffected by dipyridamole. Adenylate cyclase complexes, with their known tubulin association, are suggested as involved in a route of colchicine-entry and so could give a means whereby environmental changes modify colchicine toxicity, and colchicine-attachment to cerebral preparations.