THE DIRECT EFFECT OF NOREPINEPHRINE AND OF ANGIOTENSIN ON THE PULMONARY VEINS OF INTACT DOGS

¹ Tulane University School of Medicine, Department of Surgery, New Orleans, Louisiana

The direct response of the pulmonary veins to angiotensin and norepinephrine in intact dogs was studied by a technique of pump perfusion of a hemodynamically separated lobar artery at a constant flow. During administration, the direct effects of these pressor agents were studied in the pump-perfused lobe, whereas the modulated effects were studied in the normally perfused lobes. In the pump-perfused lobe, angiotensin actively constricted vessels upstream to the small pulmonary veins, presumably the pulmonary arteries, but had no demonstrable effect on the pulmonary veins. Although lobar arterial pressure increased, lobar venous pressure was unchanged. In normally perfused lobes, the vasoconstrictor response to angiotensin was obscured by the decrease in pulmonary blood flow. Norepinephrine actively constricted both the lobar pulmonary veins and the upstream vessels, presumably the lobar pulmonary arteries. In the normally perfused lung vessels, the response to norepinephrine was modified by increases in blood flow and blood volume. Larger doses of norepinephrine and angiotensin increased left atrial pressure and modulated the responses of lobar veins. This modulated response was compared to the passive response of the pulmonary veins to similar increases in left atrial pressure which were produced by mechanically impeding left ventricular ejection. The data indicate that, whereas the lobar veins were passively distended by the left atrial hypertension induced by norepinephrine, the compliance of these vessels decreased. The response of the lobar vein to the left atrial hypertension induced by angiotensin, however, was similar to that induced by impeding left ventricular ejection. These experiments indicate that the responses of the pulmonary veins to angiotensin and norepinephrine are similar to the responses of systemic veins to these drugs.