Reduction in accumulation of [3H]triphenylmethylphosphonium cation in neuroblastoma cells caused by optical probes of membrane potential. Evidence for interactions between carbocyanine dyes and lipophilic anions.

The accumulation of [3H]triphenylmethylphosphonium cation in neuroblastoma N1E 115 cells in the presence of tetraphenylboron is reduced by 3,3'-diethylthiadicarbocyanine iodide and by 3,3'-dipropylthiadicarbocyanine iodide. This reduction in uptake of the lipophilic cation is not due to the carbocyanine dyes depolarizing the plasma membrane of these cells but due to an interaction between the carbocyanine dyes and tetraphenylboron leaving less of the lipophilic anion free in solution to assist uptake of the lipophilic cation. This interaction is shown to have a 1:1 stoicheiometry.