The transient receptor potential vanilloid 4 (TRPV4) channel is a nonselective cation channel expressed on many cell types, including the vascular endothelium and smooth muscle cells. TRPV4 channels play a role in regulating vasomotor tone and capillary permeability. The present study was undertaken to investigate responses to the TRPV4 agonist GSK101790A on the pulmonary and systemic vascular beds in the rat. Intravenous injection of GSK1016790A at doses of 2-10 μg/kg produced dose-dependent decreases in systemic arterial pressure, small decreases in pulmonary arterial pressure, and small increases in cardiac output, and responses were not altered by the cyclooxygenase inhibitor meclofenamate or the cytochrome P-450 inhibitor miconazole. Injection of GSK1016790A at a dose of 12 μg/kg iv produced cardiovascular collapse that was reversible in some animals. GSK1016790A produced dose-related decreases in pulmonary and systemic arterial pressure when baseline tone in the pulmonary vascular bed was increased with U-46619. After treatment with the nitric oxide synthase (NOS) inhibitor N-nitro-l-arginine methyl ester, GSK1016790A produced larger decreases in systemic arterial pressure and dose-dependent increases in pulmonary arterial pressure followed by a small decrease. These results demonstrate that GSK1016790A has vasodilator activity in pulmonary and systemic vascular beds and that when NOS is inhibited, GSK1016790A produced pulmonary vasoconstrictor responses that were attenuated by the L-type Ca(2+) channel antagonist isradipine. The presence of TRPV4 immunoreactivity was observed in small pulmonary arteries and airways. The present data indicate that responses to TRPV4 are modulated differently by NOS in pulmonary and systemic vascular beds and are attenuated by the TRPV4 antagonist GSK2193874.
Keywords: hyperpolarization; lung hydrostatic pressure; pulmonary vascular bed; transient receptor potential vanilloid 4 channels; vasodilation.