The emergence of human heart-lung transplantation as a possible therapeutic modality1 raises a general problem. The donor lung must maintain viability, despite the temporary loss of pulmonary blood flow, bronchial blood flow, and ventilation. The problem that arises concerns the impact of reduced or absent blood flow on lung cell function.
Decreases in regional blood flow (ischemia) relative to metabolic requirements is an area of considerable importance. Ischemia in the systemic circulation results in limitations of both the oxygen and substrate supply, thereby altering cell tissue and organ function. Studies of systemic ischemia have provided substantial insight into the pathophysiologic features of a variety of vascular diseases.
The possible impact of reduced pulmonary blood flow (the ischemic lung) on the metabolism of lung cells has received little attention. The major function of the lung is gas exchange, and most studies of reduced pulmonary blood flow have focused on the