The influence of doxyl stearic acids (DSAs) on gap junctional conductance (g(j)) between pairs of neonatal rat heart cells was studied. DSAs are spin probes that perturb the membrane at different depths depending on position of the doxyl group on the fatty acyl chain. 16-DSA and 12-DSA rapidly and reversibly reduced g(j) to unmeasureable levels in a dose- and time-dependent manner. Single channel events observed when g(j) was low were of the same unitary size as those observed under control conditions. The methyl esters of 16- and 12-DSA, stearic acid itself, and TEMPO, an analogue of the doxyl group that has no fatty acyl chain, had no effect on g(j). Protonation of the carboxyl head group (by acidifying the solution) reduced the potency of 16- or 12-DSA. Spontaneous beating activity and action potentials were observed at concentrations of the DSAs 15-20 times that necessary for uncoupling. These results indicate that uncoupling by the DSAs requires the presence of the charged carboxyl group and localized perturbation of the channel at the lipid-channel interface by the doxyl group. Furthermore, they predict that unsaturated free fatty acids, which accumulate during ischemia, may exert their arrhythmogenic effect by reducing g(j), and thereby slowing conduction.
|Original language||English (US)|
|Journal||American Journal of Physiology - Cell Physiology|
|State||Published - 1989|
ASJC Scopus subject areas
- Cell Biology