Figure 6. Taurine effect on junctional
conductance. Exposure to 40 mM taurine had no significant effect on the
voltage sensitivity of the junctional currents recorded over the range
of ±80 mV, although there was a slight current reduction at negative
junctional voltages. The data (n=4 for each condition) were fit by the
Boltzmann equation: Gjss = { (Gjmax – Gjmin
) / ( 1 + exp [A ( Vj –Vo ) ] } + Gjmin
where
Gjmax (normalized to unity) is the maximum conductance, Gjmin
is the residual conductance at large values of Vj, and Vo
is the Vj at which Gjss = (Gjmax–Gjmin)/2.
The constant A (A=nq/kT) represents the voltage sensitivity in terms of
gating charge as the equivalent number (n) of electron charges (q)
moving through the membrane, k is the Boltzmann constant, and T is the
absolute temperature. As shown in the inset, taurine had no significant
effect on the junctional conductance between paired oocytes expressing
this gap-junctional protein (p=0.5444 by Student’s t-test), and
there were no significant differences in the values of A for taurine
treated and control oocytes in either the positive or negative branches
of the curves. These findings are a good indication that taurine does
not affect Cx43 gap junctional channels.