Release of endothelin in the oleic acid-induced respiratory distress syndrome in rats.

Rats injected intravenously with oleic acid developed pulmonary edema leading to hypoxia and hypercarbia. These changes were accompanied by an increase in immunoreactive endothelin (ir-ET) in plasma as early as 15 min after injection. At 45 min after injection plasma levels peaked at 114 +/- 19 pg/ml plasma (n = 8) and reached basal levels again after 240 min. In contrast, much larger amounts of ir-ET were found in the bronchoalveolar lavage fluid, with a peak at 120 min (2878 +/- 258 pg/lung, n = 7) preceding the maximum hypoxia observed at 180 min. In both plasma and bronchoalveolar lavage fluid samples ir-ET was characterized by reverse-phase HPLC as a mixture consisting mainly of ET-1 and smaller amounts of big ET-1, ET-2 and ET-3. In light of the biological effects of ET, the data suggest that these peptides might be of pathophysiological significance in this model of adult respiratory distress syndrome.