P433

         Bull Eur Physiopathol Respir 1982 Sep-Oct;18(5):687-92

        Effect of alpha-methyldopa on lung microembolism in the rat.

        Herget J, Suggett AJ, Palecek F, Slavik Z.

        The effect of chronic pretreatment with alpha-methyldopa on acute

        pulmonary hypertension induced by lung microembolization with Sephadex

        particles in the rat was studied. Alpha-methyldopa was administered

        twice a day for 10 days by oesophageal gavage (20 mg X kg-1 of body

        weight) prior to embolization. Rats were anaesthetized with urethane. A

        catheter was positioned in closed chest rats in the pulmonary artery and

        50 microliter of Sephadex suspension in saline were injected. The

        control group was not pretreated with alpha-methyldopa. In a subgroup of

        control and pretreated rats, the cardiac output was measured by the dye

        dilution technique before and after lung microembolization. Rats

        pretreated with alpha-methyldopa had less pulmonary hypertension, higher

        cardiac output and more severe arterial hypoxaemia 15 min after lung

        microembolization than untreated animals. There was no difference in

        platelet counts prior and after embolization. We suggest that pulmonary

        hypertension after lung microembolization in the rat includes a

        vasoconstrictor component which can be suppressed by alpha-methyldopa,

        and that severe arterial hypoxaemia in pretreated rats is probably the

        result of a decrease of the ventilation/perfusion ratio in unobstructed

        areas, which in untreated rats may be prevented by active

        vasoconstriction.