Mechanism of peptidoleukotriene-induced increases in pulmonary transvascular fluid filtration.

We examined the effects of leukotrienes C4 (LTC4) and D4 (LTD4) (1 microgram) on the pulmonary vascular filtration coefficient, a measure of vessel wall conductivity to water, and the alterations in pulmonary vascular resistance (PVR) in isolated-perfused guinea pig lungs. We also assessed whether LTC4 and LTD4 increased the permeability to albumin in cultured monolayers of pulmonary artery endothelial cells. In Ringer-perfused and blood-perfused lungs, LTC4 resulted in increases in pulmonary arterial pressure (Ppa) and the pulmonary capillary pressure (Pcap) measured as the equilibration pressure after simultaneous pulmonary arterial and venous occlusions. Pulmonary venous resistance (Rv) increased to a greater extent than arterial resistance (Ra) in both Ringer-perfused and blood-perused lungs challenged with LTC4. The greater increase in PVR in blood-perfused lungs corresponded with a greater elevation of lung effluent thromboxane B2 (TxB2) concentration. The LTC4-stimulated increase in PVR was prevented by pretreatment with meclofenamate (10(-4) M). LTD4 also induced rapid increases in Ppa and Pcap in both Ringer-perfused and blood-perfused lungs; however, Ppa decreased before stabilizing at a pressure higher than base line. The increases in Rv with LTD4 were greater than Ra. The LTD4-stimulated increases in Ra and Rv also paralleled the elevation in TxB2 concentration. As with LTC4, the increases in Ppa, Pcap, PVR, and TxB2 concentration were greater in blood-perfused than in Ringer-perfused lungs. Pretreatment with meclofenamate reduced the magnitude of the initial increase in Ppa, but did not prevent the response.(ABSTRACT TRUNCATED AT 250 WORDS)