Table 1.
Summary of smooth myocyte conventional and perforated-patch whole cell, and single-channel recordings
| LTH |
NXa |
|||
|---|---|---|---|---|
| Adult | Fetus | Adult | Fetus | |
| Capacitance, pF | ||||
| Conventional whole-cell | 15.2 ± 0.9 (6) | 8.3 ± 0.4 (7)* | # | # |
| Perforated-patch | 16.1 ± 1.3 (7) | 9.4 ± 1.7 (6)* | 15.7 ± 0.6 | 9.1 ± 0.6** |
| Current density, pA/pF | ||||
| Conventional whole-cellb | ||||
| Outward current | 54.2 ± 4.1 (7) | 24.8 ± 3.0 (8)** | # | # |
| BK current | 25.7 ± 3.4 | 11.2 ± 2.2* | # | # |
| Non-BK current | 28.8 ± 3.2 | 13.6 ± 2.3* | ∼29a | ∼26a |
| Perforated-patchb | ||||
| Outward current | 75.1 ± 5.9 (5) | 71.6 ± 13 (6) | 37.9 ± 1.8 | 57.9 ± 6.7* |
| BK current | 46.3c | 58.0c | 10a | 29a |
| Resting membrane potential, mV | −28.7 ± 5.5 (8) | −39.4 ± 7.0 (8)* | −30.1 ± 4.0(13) | −23.8 ± 2.6 (17) |
| BK single-channel parameters | ||||
| Slope, mV/log [Ca2+]i | 65.9 ± 3.3 | 66.8 ± 3.8 | 67.1 ± 2.5 | 67.6 ± 2.7 |
| Ca2+ set point, Cao, μM | 3.6 | 3.0 | 8.8 | 4.7 |
| Hill coefficient, rH | 3.3 ± 0.2 | 3.0 ± 0.3 | 2.9 ± 0.1 | 2.9 ± 0.2 |
| Unitary conductance, pS | 215 ± 12 | 228 ± 7 | 221 ± 8 | 229 ± 5 |
Values are means ± SE, based on a sample size of (n). Conventional (Fig. 1) and perforated-patch (Fig. 9) whole-cell recording yield membrane capacitance and current density. Single-channel recording and analysis (Fig. 2) reveal large-conductance Ca2+-activated K+ (BK) channel parameters and properties. LTH, long-term hypoxia; NX, normoxic.
a
From Lin et al. (33);
b
measured at +60 mV;
c
estimated by subtracting Non-BK current from perforated-patch outward current;
#
not measured. When compared against adult of same treatment:
*
P < 0.05;
**
P < 0.01.