K ATP Channels Mediate CGRP‐Dependent Hyperpolarization of Mouse Pulmonary Artery Smooth Muscle and Endothelium

Calcitonin gene related peptide (CGRP) hyperpolarizes membrane potential (V m ) of smooth muscle cells (SMCs) and endothelial cells (ECs) in pulmonary arteries (PAs) ( FASEB J . 30, 945.18). In the systemic circulation, protein kinase A (PKA) can phosphorylate ATP‐sensitive potassium channels (K ATP ) as a mechanism of vasodilation to CGRP. We hypothesized that this signaling pathway is effective in the pulmonary circulation. Intact PAs were isolated (internal diameter, ~150 μm) from male C57BL/6J mice (age, 3 months), cannulated, pressurized to 16 cm H 2 O, and studied at 37°C. Alternatively, intact endothelial tubes were studied at 32°C following dissociation of SMCs. V m was recorded continuously using intracellular microelectrodes. At rest, V m was −43±2 mV for SMCs of intact PAs and −38±1 mV for ECs in endothelial tubes. Increasing concentrations (1 nM to 10 μM) of pinacidil (K ATP activator) hyperpolarized SMCs by 38±2 mV (to −80±3 mV) and ECs by 36±3 mV (to −73±3 mV); respective EC 50 values were 72 and 40 nM (n=4/group). Hyperpolarization of SMCs and ECs with 10 μM pinacidil was reversed by glibenclamide (K ATP inhibitor) in a concentration‐dependent manner, with complete reversal at 1 μM. Increasing [CGRP] from 0.1 nM to 1 μM hyperpolarized SMCs of intact PAs by 17±3 mV (to −52±3 mV) and ECs by 20±4 mV (to −57±3 mV). With no effect on resting V m , 1 μM glibenclamide attenuated (P<0.05) hyperpolarization of both SMCs (4±1 mV; n=5) and ECs (5±3 mV; n=4) to 1 μM CGRP. Inhibiting PKA with protein kinase inhibitor [PKI (14–22) amide, myristoylated; 10 μM] attenuated hyperpolarization to 1 μM CGRP in SMCs (5±1 mV; n=3) and in ECs (4±2 mV; n=4). In PAs preconstricted to ~50% of resting diameter with 5 μM uridine triphosphate, peak dilation to 1 μM CGRP was 87±4% (n=5) and 1 μM glibenclamide attenuated this effect to 14±5% (n=4). We conclude that CGRP‐dependent hyperpolarization of pulmonary arterial SMCs and ECs is mediated by K ATP channel activation via PKA, leading to vasodilation. These findings provide mechanistic insight into therapies for vascular diseases associated with impaired pulmonary perfusion. Support or Funding Information Support: NIH R37HL041026