title: Effect of 5-fluorouracil and thymidine on the transmembrane potential and zeta potential of HeLa cells.
abstract: The main result of the experiments reported in this paper is the observation that HeLa cells, when treated with 5-fluorouracil (5-FU), show a damped oscillatory response in the transmembrane potential. This effect is counteracted by thymidine. Damped oscillation in the transmembrane potential occurs within the first hr after addition of 5-FU, commencing with an initial hypopolarization. At low concentrations (10(-8) through 10(-7) M), hyperpolarization of the cell membrane is observed after lengthy incubation time (24 to 96 hr). Membrane depolarization is enhanced at higher concentrations (10(-6) through 10(-4) M) and with increasing exposure to the cytostatic substance. The surface charge or zeta potential of HeLa cells is altered to a lesser extent by 5-FU than is the transmembrane potential. Distinct effects can be observed as late as after 72 and 96 hr. When thymidine (2 x 10(-5) M) is added along with 5-FU, the depolarizing action of the antimetabolite can be abolished. Thymidine itself, at the concentration used, causes almost no change in membrane polarization. The results suggest that the effect of 5-FU on the cell membrane is related to the influence of the antimetabolite on cell growth. Moreover, this membrane effect might be the primary cause for the cytostatic action.
mesh_terms: D002462:Cell Membrane / Q000187:drug effects; D005472:Fluorouracil / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006367:HeLa Cells / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects*; D013936:Thymidine / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D005472:Fluorouracil; D013936:Thymidine