Fig. 2.
Response of DTT-treated or 4,4′-DTDP-treated RyR2 channels to changes in luminal (trans) [Ca2+]. (A–F) Effects of DTT treatment. (A) 3 s of single channel activity at +40 mV, where channel opening is upward from zero current (‘C’, continuous line) to maximum open conductance (‘O’, broken line) with a cytoplasmic [Ca2+] of 1.0 µM. Open probability (Po) values for each recording are shown. Descending from the upper trace, the data show initial activity with 1.0 mM luminal Ca2+, activity after adding 1 mM DTT to the cytoplasmic solution, activity following luminal perfusion with a 0.1 mM Ca2+ solution, then activity when luminal [Ca2+] was increased stepwise to 0.5 mM, 1 mM and 1.5 mM. (B) Mean Po before and after adding 1 mM DTT (n = 14). Ctrl, control. (C–F) Mean data (n = 6–14) for Po (C); mean open time (To) (D); mean closed time (Tc) (E); and mean open frequency (Fo) (F). (G–L) Effects of 4,4′-DTDP-treatment. (G) 3 s of single channel activity at −40 mV, where channel opening is downward from zero current (‘C’, continuous line) to maximum open conductance (‘O’, broken line) with a cytoplasmic [Ca2+] of 1.0 µM. Descending from the upper trace, the data show initial activity with 1.0 mM luminal Ca2+, activity after adding 20 µM 4,4′-DTDP to the cytoplasmic solution, activity following luminal perfusion with a 0.1 mM Ca2+ solution, then activity when luminal [Ca2+] was increased stepwise to 0.5 mM, 1 mM and 1.5 mM. Po values for each recording are shown. (H) Mean Po before and after adding 20 µM 4,4′-DTDP (n = 10). (I–L) Mean data (n = 6–14) for (I) Po, (J) To, (K) Tc and (L) Fo. Error bars show ±s.e.m.; *P<0.05 (versus the value with 0.1 mM Ca2+).