Role of the NP-cGMP-PKG pathway in dendroaspis natriuretic peptide-induced inhibition of delayed rectifier potassium current

AIM: To investigate the role of the natriuretic peptide (NP)-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway in dendroaspis natriuretic peptide (DNP)-induced inhibition of delayed rectifier potassium currents (I_K(V)) in gastric antral circular smooth muscle of guinea pigs and to explore potential mechanisms involved.

METHODS: The whole cell patch-clamp technique was used to record delayed rectifier potassium current (I_K(V)) and to investigate the role of the NP-cGMP-PKG pathway in DNP-induced inhibition of I_K(V) in gastric myocytes isolated by collagenase digestion.

RESULTS: DNP significantly inhibited I_K(V) in a concentration-dependent manner. DNP at concentrations of 0.01, 0.1 and 1 µmol/L (at 60 mV) decreased I_K(V) to 83.5% ± 2.1%, 71.8% ± 2.3% and 63.8 ± 2.2% of control level, respectively. LY83583 (0.1 µmol/L), a guanylate cyclase inhibitor, significantly impaired DNP (1 µmol/L)-induced inhibition of I_K(V) (63.8% ± 2.2% vs 76.8% ± 2.3%) at 60 mV. Moreover, DNP-induced inhibition of I_K(V) was potentiated by zaparinast (1 µmol/L), a cGMP-sensitive phosphoesterase inhibitor (63.8% ± 2.2% vs 56.8% ± 2.1%). DNP-induced inhibition of I_K(V) was completely blocked by KT5823, an inhibitor of cGMP-dependent PKG, but not affected by KT-5720, a protein kinase A (PKA)-specific inhibitor.

CONCLUSION: DNP inhibits I_K(V) in a NP-cGMP-PKG pathway-dependent and cAMP/PKA pathway-independent manner. I_K(V) may play a critical role in regulating resting membrane potential in the gastric antral circular myocytes of guinea pigs.