Journal of Applied Physiology, Vol 60, Issue 1 38-44, Copyright © 1986 by American Physiological Society
Effect of isoproterenol or exercise on pulmonary lymph flow and hemodynamics
H. O'Brodovich and G. Coates
Experiments were performed to determine whether different methods of
increasing cardiac output would have similar effects on lung lymph flow,
and to assess the contribution of the microvasculature (fluid-exchanging
vessels) to the total calculated pulmonary vascular resistance. Yearling
unanesthetized sheep with chronic vascular catheters and lung lymph
fistulas underwent intravenous infusions of isoproterenol at 0.2 micrograms
X kg-1. min-1 (n = 8) or were exercised on a treadmill (n = 16). Both
isoproterenol and exercise increased cardiac output, lowered calculated
total pulmonary and systemic vascular resistances, and had no effect on the
calculated pulmonary microvascular pressure. Isoproterenol infusions did
not affect lung lymph flow, whereas exercise increased lung lymph flow in
proportion to the increase in cardiac output. We conclude that 1) the sheep
has a different pulmonary hemodynamic response to exercise than dogs and
man, 2) the microvasculature is recruited during exercise-induced but not
isoproterenol-induced increases in cardiac output, and 3) the
microvasculature represents only a small proportion of the total calculated
pulmonary vascular resistance.
