Purinoceptors in the pulmonary circulation of the rat and their role in hypoxic vasoconstriction

P 2 ‐purinoceptors have been characterized in the systemic circulation of a variety of species but little is known about their nature in the pulmonary vasculature. In the isolated, blood perfused and ventilated lung of the rat the P 2x selective analogues α,β‐methylene ATP(α,β‐meATP) (25 μg) and β,γ‐methylene ATP (400 μg) caused a rise in pulmonary artery pressure (127 ± 32% and 110 ± 23% increase respectively, n = 6), demonstrating the existence of vasoconstrictor P 2 receptors in the pulmonary circulation. Repeated boluses of α,β‐meATP resulted in complete desensitization of the constrictor response to β,γ‐meATP, but a small vasodilator response remained indicating unopposed stimulation of P 2y receptors. The desensitization by α,β‐meATP had no effect on angiotensin II‐induced vasoconstriction. After desensitization of the vasoconstrictor P 2 receptors with α,β‐meATP, hypoxic pulmonary vasoconstriction remained intact, indicating that these receptors are not involved in this response.