AJP - Heart and Circulatory Physiology, Vol 242, Issue 4 645-H651, Copyright © 1982 by American Physiological Society
Effect of ADP-induced platelet aggregation on lung fluid balance in sheep
F. L. Minnear, D. G. Moon, J. E. Kaplan and A. B. Malik
The effects of platelet aggregation (PA), induced by an intravenous
injection of adenosine 5'-diphosphate (ADP), on pulmonary fluid and protein
exchange and on arterial blood gases were determined in artificially
ventilated sheep prepared with lung lymph fistulas. ADP injection produced
small increases (P less than 0.01) in pulmonary lymph flow (Qlym) and
transvascular protein clearance (Qlym X lymph-to-plasma protein
concentration ratio). These changes were not associated with significant
increases in pulmonary arterial and left atrial pressures, pulmonary blood
flow, or pulmonary vascular resistance. ADP-induced PA did not increase the
pulmonary endothelial permeability to proteins, because an elevation of
pulmonary microvascular pressure (Pmv), induced by inflation of a left
atrial balloon catheter, produced the same increases in Qlym and protein
clearance as in normal sheep after comparable increases in Pmv. The
increases in Qlym and protein clearance can be explained by an increase in
pulmonary vascular surface area. ADP-induced PA decreased the arterial
oxygen tension, which was sustained for the 3 h duration of the study; the
arterial carbon dioxide tension did not change and the arterial pH
decreased (P less than 0.05) after PA. Chronic depletion of platelets with
antiplatelet serum prevented the increases in Qlym and protein clearance
and the arterial hypoxemia, indicating that these changes were the direct
result of PA. Thus ADP-induced PA in sheep increased pulmonary fluid
filtration and protein clearance by an increase in the vascular surface
area. Also PA produced a rapid and prolonged arterial hypoxemia, which may
result from the release of vasoactive and bronchoactive factors causing a
maldistribution of ventilation and perfusion.
