Neonatal Rat Cardiomyocytes Show Characteristics of Nonhomotypic Gap Junction Channels

Figures & data

Figure 1 Immunocytochemical staining of neonatal rat cardiomyocytes (anti-Cx40, anti-Cx43, and anti-Cx45 stained) and Western Blot analysis (detection of Cx40, Cx43, Cx45, and GAPDH). All three connexins are expressed and assemble in the cell membrane (see arrows). Scale bar = 10 μ m.

Figure 2 Original superimposed traces for voltage of the pulsed cell V₁, voltage of the nonpulsed cell V₂ = −40 mV and current recorded in the non-pulsed cell I₂. Junctional conductance (G_j) is calculated as follows: G_j = I₂/V_jwith the transjunctional voltage difference V_j = V₂ − V₁.

Figure 3 (a–c) Summarized data gained from Cx40-, Cx43-, and Cx45-transfected HeLa cells showing dependence of gap junction conductance on junctional potential V_j with a quasisymmetrical relationship for g_{j (normalized)} = f (V_j). Average instantaneous gap junction conductance of each group was (mean ± SEM): HeLa Cx40: Gj = 5.18 ± 1.89 nS, n = 8; HeLa Cx43: Gj = 12.24 ± 2.92 nS, n = 9; HeLa Cx45: Gj = 2.84 ± 1.24, n = 10.

TABLE 1 Inactivation parameters

Cell pairs	V0	gmin
HeLa Cx40	−46.68/55.10	0.52/0.55
HeLa Cx43	−78.28/71.99	0.48/0.46
HeLa Cx45	−25.65/18.37	0.22/0.21

Note. The inactivation parameters V₀ and g_min are obtained from curve fitting to the Boltzmann equation (Equation 1) of the summarizeded data for all investigated groups of cell pairs.

Figure 4 Summarized data gained from neonatal rat cardiomyocytes showing dependence of gap junction conductance on junctional potential V_j with an asymmetrical relationship for g_{j(normalized)} = f(V_j). Average instantaneous gap junction conductance was (mean ± SEM): Gj = 14.01 ± 2.41 nS, n = 16.

Figure 5 Examples taken from separate recordings of neonatal rat cardiomyocyte cell pairs with (a) quasisymmetrical gating behavior and (b) asymmetrical gating behavior.