Findings. All three ENaC subunits are clearly expressed in AQP2-positive

Findings. All three ENaC subunits are clearly expressed in AQP2-positive cells of the ASDN in both control and Adx mice. This finding is in agreement with what has been reported for the expression ofTable 1. ENaC activity in control and Adx miceDrinking water Control H2O 1 saline H2O 1 saline H2O 1 saline Adx H2O 1 saline H2O 1 saline 1 saline Treatment — — DOCA DOCA AVP Tolvaptan — — DOCA DOCA Tolvaptan 0.78 0.25 1.4 0.76 1.78 0.13 1.4 0.53 1.6 0.76 0.17 NPo ???????????0.17* 0.06 0.22*,** 0.15** 0.17** 0.04 0.59* 0.11+ 0.21* 0.10 0.04*Adx mice with 1 saline compared with tap water offered some protection, as expected (6, 9, 22?6), against the volume depletion and hyponatremia of their hypoadrenal, sodium- and water-wasting state. To test whether a functional adrenal gland–and, thus, the ability to have dynamic mineralocorticoid signaling–is an absoluteN 2.4 1.5 3.0 2.7 3.8 1.4 4.1 2.0 3.8 2.2 1.7 ???????????0.30* 0.19 0.40 0.35** 0.42** 0.15 0.90*,+ 0.20 0.40* 0.19 0.16 0.28 0.15 0.44 0.22 0.44 0.08 0.23 0.22 0.36 0.31 0.09 ???????????Po 0.03* 0.03 0.04*,** 0.02** 0.03** 0.02 0.02 0.03 0.05** 0.03** 0.01* 0.46 0.39 0.60 0.56 0.75 0.31 0.44 0.50 0.65 0.65 0.f (36/79) (20/51) (29/48) (33/59) (30/40)** (19/62) (10/23) (26/52) (35/54) (32/49) (33/96)All groups were maintained with regular chow containing 0.32 [Na+]. *Significant increase/decrease compared with 1 saline drinking water. **Significantly greater compared with no treatment. +Significantly greater compared with control mice under identical conditions. Injected with 2.4 mg of DOCA (in 150 L of olive oil) for 3 consecutive days or treated with 30 mg/kg Tolvaptan added to drinking water for 2 d before patch-clamp analysis or isolated ASDN treated with 1 M AVP for at least 30 min before patch-clamp analysis. f, frequency (patches with at least one active channel/total number of viable seals for that condition) compared with a z test.10096 | www.pnas.org/cgi/doi/10.1073/pnas.Mironova et al.0.6 Po 0.= + DOCA**0.0.0 control Adxresponsiveness to changes in sodium balance (21). Because changes in sodium intake do not change Po in mice with compromised adrenal function, ENaC is less responsive to this perturbation in Adx mice. Exogenous mineralocorticoid clamps ENaC activity high in both groups, disrupting normal feedback regulation to the channel in response to changes in sodium intake, which is shown as LM22A-4MedChemExpress LM22A-4 elevations in fractional ENaC activity [in the presence of Isorhamnetin web deoxycorticosterone acetate (DOCA)].Adrenal Insufficiency Increases Plasma [AVP]. The above results demonstrate that some regulatory factor stimulates ENaC in the absence of adrenal steroids in Adx mice. We tested first whether AngII could function in this regard, and results were negative. The finding that plasma [AVP], as shown in Fig. 5, is significantly increased in Adx compared with control mice–maintained with normal chow and tap water–identifies this hormone as a potential candidate mediating this effect. This observation that loss of adrenal gland function increases plasma [AVP] is consistent with the findings of others (22, 27?9). AVP Increases ENaC Activity. To test whether AVP can serve as a stimulator of ENaC activity in the absence of adrenal gland function, we assessed the actions of this neurohormone on channel activity as shown in Fig. 6 (see also Table 1). As can be seen clearly in the summary graphs of Po (Fig. 6A), N (Fig. 6B), and NPo (Fig. 6C), AVP significantly increases ENaC activity by.Findings. All three ENaC subunits are clearly expressed in AQP2-positive cells of the ASDN in both control and Adx mice. This finding is in agreement with what has been reported for the expression ofTable 1. ENaC activity in control and Adx miceDrinking water Control H2O 1 saline H2O 1 saline H2O 1 saline Adx H2O 1 saline H2O 1 saline 1 saline Treatment — — DOCA DOCA AVP Tolvaptan — — DOCA DOCA Tolvaptan 0.78 0.25 1.4 0.76 1.78 0.13 1.4 0.53 1.6 0.76 0.17 NPo ???????????0.17* 0.06 0.22*,** 0.15** 0.17** 0.04 0.59* 0.11+ 0.21* 0.10 0.04*Adx mice with 1 saline compared with tap water offered some protection, as expected (6, 9, 22?6), against the volume depletion and hyponatremia of their hypoadrenal, sodium- and water-wasting state. To test whether a functional adrenal gland–and, thus, the ability to have dynamic mineralocorticoid signaling–is an absoluteN 2.4 1.5 3.0 2.7 3.8 1.4 4.1 2.0 3.8 2.2 1.7 ???????????0.30* 0.19 0.40 0.35** 0.42** 0.15 0.90*,+ 0.20 0.40* 0.19 0.16 0.28 0.15 0.44 0.22 0.44 0.08 0.23 0.22 0.36 0.31 0.09 ???????????Po 0.03* 0.03 0.04*,** 0.02** 0.03** 0.02 0.02 0.03 0.05** 0.03** 0.01* 0.46 0.39 0.60 0.56 0.75 0.31 0.44 0.50 0.65 0.65 0.f (36/79) (20/51) (29/48) (33/59) (30/40)** (19/62) (10/23) (26/52) (35/54) (32/49) (33/96)All groups were maintained with regular chow containing 0.32 [Na+]. *Significant increase/decrease compared with 1 saline drinking water. **Significantly greater compared with no treatment. +Significantly greater compared with control mice under identical conditions. Injected with 2.4 mg of DOCA (in 150 L of olive oil) for 3 consecutive days or treated with 30 mg/kg Tolvaptan added to drinking water for 2 d before patch-clamp analysis or isolated ASDN treated with 1 M AVP for at least 30 min before patch-clamp analysis. f, frequency (patches with at least one active channel/total number of viable seals for that condition) compared with a z test.10096 | www.pnas.org/cgi/doi/10.1073/pnas.Mironova et al.0.6 Po 0.= + DOCA**0.0.0 control Adxresponsiveness to changes in sodium balance (21). Because changes in sodium intake do not change Po in mice with compromised adrenal function, ENaC is less responsive to this perturbation in Adx mice. Exogenous mineralocorticoid clamps ENaC activity high in both groups, disrupting normal feedback regulation to the channel in response to changes in sodium intake, which is shown as elevations in fractional ENaC activity [in the presence of deoxycorticosterone acetate (DOCA)].Adrenal Insufficiency Increases Plasma [AVP]. The above results demonstrate that some regulatory factor stimulates ENaC in the absence of adrenal steroids in Adx mice. We tested first whether AngII could function in this regard, and results were negative. The finding that plasma [AVP], as shown in Fig. 5, is significantly increased in Adx compared with control mice–maintained with normal chow and tap water–identifies this hormone as a potential candidate mediating this effect. This observation that loss of adrenal gland function increases plasma [AVP] is consistent with the findings of others (22, 27?9). AVP Increases ENaC Activity. To test whether AVP can serve as a stimulator of ENaC activity in the absence of adrenal gland function, we assessed the actions of this neurohormone on channel activity as shown in Fig. 6 (see also Table 1). As can be seen clearly in the summary graphs of Po (Fig. 6A), N (Fig. 6B), and NPo (Fig. 6C), AVP significantly increases ENaC activity by.