Fig. 4.
Regulation of αβγ-ENaC activity by PKG isoform-specific modulators. A: effects of PKGI and PKGII activators on ENaC activity. 8-pCPT-cGMP (CPT-cGMP) was a cell-permeable PKG activator, predominantly activating PKGII isoform. Sp isomer of β-phenyl-1,N2-etheno-8-bromo-cGMP (Sp-8-Br-PET-cGMP) was a specific PKGI (both I-α and I-β) activator. Oocytes were perfused with 8-pCPT-cGMP, and then it was washed out, followed by application of Sp-8-Br-PET-cGMP. *P < 0.05. n = 6. B: blockade of the stimulating effect in oocytes pretreated with PKG inhibitor. Cells were pretreated with 250 μM Rp-8-Br-cGMP to block both PKGI and PKGII for 1 h at room temperature. n = 6. C: competition of standard cGMP (Std cGMP) and 8-pCPT-cGMP. The activation efficacy of 8-pCPT-cGMP (ICPT-cGMP/Ibasal) was compared in the absence and presence of standard cGMP. P > 0.05. D: PKG enzymatic activity. Normalized PKG activity in oocytes was incubated with vehicle (Control), 8-pCPT-cGMP (0.2 mM), Rp-8-Br-cGMP (0.5 mM), or both for 1 h. **P < 0.01 compared with control. Numbers in parentheses, number of oocytes examined for each group.