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Effects of Colchicine on Cyclic AMP Levels in Human Leukocytes
Stephen A. Rudolph, Paul Greengard and Stephen E. Malawista
Proceedings of the National Academy of Sciences of the United States of America
Vol. 74, No. 8 (Aug., 1977), pp. 3404-3408
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/66949
Page Count: 5
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The increase in human leukocyte adenosine 3′:5′-cyclic monophosphate (cyclic AMP) levels seen in response to various substances was markedly potentiated by colchicine and other agents that affect microtubule assembly. Addition of dl-isoproterenol (2 μ M) or prostaglandin E1 (10 μ M), together with the phosphodiesterase inhibitor isobutylmethylxanthine (1 mM), caused a much greater increase in cyclic AMP in colchicine-pretreated cells than in control cells. With isoproterenol (2 μ M) plus isobutylmethylxanthine (1 mM), cyclic AMP levels rose about 3-fold but, in combination with colchicine, these drugs caused a more than 15-fold increase in cyclic AMP. The effects of colchicine were both time-and dose-dependent; they could be seen within 1 min after addition of colchicine or at concentrations as low as 10 nM. In addition to its potentiation of hormonally induced increases in cyclic AMP levels, colchicine also potentiated the effect of isobutylmethylxanthine alone on leukocyte cyclic AMP levels. Vinblastine, vincristine, podophyllotoxin, and oncodazole all had effects similar to those of colchicine but lumicolchicine did not. The data suggest that cytoplasmic microtubules interact with the leukocyte plasma membrane to impose constraints on the expression of hormone-sensitive adenylate cyclase; the therapeutic effects of colchicine may depend in part upon the relaxation of such constraints. Moreover, the synergism described here between colchicine-like agents and hormones is of potential therapeutic importance in clinical conditions in which either alkaloid or hormone has been useful separately.
Proceedings of the National Academy of Sciences of the United States of America © 1977 National Academy of Sciences