Pulmonary vasodilator action of ligustrazine, active principle of a traditional Chinese remedy, in rats and ferrets.

The action of ligustrazine on the pulmonary circulation was tested in isolated perfused rat lung in vitro and autoperfused ferret lower left lobe preparation in vivo. Ligustrazine reduced hypoxic pulmonary vasoconstriction in a dose-dependent manner. It had a lesser dilator effect on KCl-induced vasoconstriction than verapamil and a relatively small inhibitory effect on the pressor response to angiotensin II. Ligustrazine preferentially inhibited the vasoconstriction caused by hypoxia and almitrine. The increased slope and intercept of the pressure-flow line caused by hypoxic vasoconstriction was reduced to the normal range after administration of ligustrazine (4 mg). Thus ligustrazine proved to be a powerful pulmonary vasodilator; it had a relatively small depressor effect on systemic blood pressure.