Dependence of junctional conductance on proton, calcium and magnesium ions in cardiac paired cells of guinea-pig.

摘要: 1. The dependence of gap junctional conductance on the intracellular concentrations H+, Ca2+ and Mg2+ was studied in paired myocytes dissociated enzymatically from guinea-pig ventricle. To apply an internal solution buffered to specific or concentration directly one aspect junction, non-junctional membrane pair mechanically ruptured. measured by clamping potential other cell using a two-pipette voltage-clamp method. 2. kept low comparison with that (less than 1/50) replacing both external K+ Cs+. 3. current-voltage (I-V) relation linear over range examined (from -100 +100 mV). No voltage time detected. 4. junction between cells ranged 90 3900 nS peak distribution at 1000 nS. 5. effect H+ pH 7.4-5.4, while keeping free-Ca2+ zero, pCa 6.3 7.0 2-10 mM-EGTA. almost constant 7.4 6.5 decreased dose-dependent manner further acidification. There no difference pH-conductance relationships various concentrations. Hill coefficient approximately 2.4 half-maximum (pK'H) 6.1. 6. closing channel 7 5, 7.4, 6.5. At each pH, increasing similar coefficients about 3.4. pCa-conductance relationship shifted toward higher as lowered (pK'Ca = 6.6, 6.4 5.6, 6.5, respectively). 7. Increasing also caused fall pMg 3.0-2.0 pK'Mg 2.5 (3.2 mM), 3.0. 8. These results suggest there are two respective binding sites for divalent cations is regulated reversibly ligand-receptor reactions. Comparing threshold electrical uncoupling, it concluded plays more important role regulating cardiac under physiological conditions.