IN-VITRO EFFECTS OF COLCHICINE ON HUMAN ERYTHROCYTE-MEMBRANES - AN ESR STUDY

Colchicine (CC) is an antimitotic and antitubular agent which is curre ntly used in medicine as a drug to treat various diseases. In spite of its widespread use the interaction of this drug with membranes is not yet known clearly. To characterize alterations in membrane molecular dynamics produced by CC, human erythrocytes were spin-labeled with 5-d oxylstearic acid (5-DSA) and 16-doxylstearic acid (16-DSA), and membra ne fluidity was quantified by measuring the changes in the order param eter (S) which reflects the anisotropy due to restricted motional aver aging, correlation time (tau(c)) representing the spin label tumbling rate in the sample and phase transitions derived from ESR measurements . CC induced significant changes in both order parameter and correlati on time at the surface of 5-DSA labeled membrane, but this was not the case at the core of 16-DSA labeled membrane. Order parameter, S and r otational correlation time, tau(c), showed a biphasic character in the temperature range of 5-50 degrees C. This fact was used to calculate phase transition temperatures and activation energies of untreated (co ntrol) and treated erythrocyte cells with CC.