Journal of Applied Physiology, Vol 51, Issue 4 875-880, Copyright © 1981 by American Physiological Society
Plasma and platelets potentiate a hypoxic vascular response of the isolated lung
S. Kivity and J. F. Souhrada
To determine whether plasma and /or platelets play a role in the hypoxic
response of pulmonary circulation, we perfused isolated rat lungs with
different concentrations of plasma and varying numbers of platelets. As the
lungs were perfused with a constant flow (8-13 ml/min), a change in the
mean pulmonary artery perfusion pressure (PApP) during acute alveolar
hypoxia was a measure of increased tone of the pulmonary circulation. It
was found that the presence of plasma in the perfusate (both 20% and 100%)
significantly (P less than 0.05) potentiated the PApP response during
repeated acute alveolar hypoxia, compared with the response to artificial
perfusate without plasma. An isolated rat lung perfused with 6.5% dextran
or 3% albumin (both in a physiological salt solution) showed only minimal
pressure response during acute alveolar hypoxia. In the second part of the
experiment, isolated lungs were perfused with a fresh 100% plasma
containing different numbers of platelets. A dose-response-like
relationship was observed between the number of platelets in the perfusate
and the response of the pulmonary vasculature to acute hypoxia. The highest
hypoxic response of the pulmonary vessels, as indicated by the increase in
PApP, was shown when the perfusate contained a nearly normal in vivo number
of platelets. It can be concluded that both plasma and platelets are
important factors that can significantly alter the hypoxic response of the
pulmonary vasculature in isolated rat lungs.
