Oxidant injury increases cell surface receptor binding of angiotensin II to pulmonary artery endothelial cells.

Nitrogen dioxide (NO2), an environmental oxidant, is known to activate phospholipase A1 and modulate the plasma membrane structure of porcine pulmonary artery endothelial cells. We evaluated the effects of exposure to NO2, purified phospholipase B (which acts as phospholipase A1 and A2), or phospholipase A2 on 125I-angiotensin II (Ang II) receptor binding, internalization, or both in pulmonary endothelial cells. Exposure to 5 ppm NO2 for 48 hr at 37 degrees C or 0.075 U each of phospholipase B or A2 in phosphate-buffered saline (PBS) for 30 min at 24 degrees C resulted in an increase in total Ang II binding (i.e., cell surface bound and internalized) by 45% (p less than 0.05), 50% (p less than 0.05), and 85% (p less than 0.001), respectively, compared to controls. An Ang II receptor antagonist, [Sar1 Ile8] Ang II, competitively displaced Ang II binding to control, NO2-, phospholipase B-, and phospholipase A2-exposed cells. Dissociation of bound Ang II in the presence of PBS was less than 1% of total bound Ang II in control, NO2-, and phospholipase B-exposed cells and was 50% of total bound Ang II in phospholipase A2-exposed cells. In the presence of isotonic acetic acid/NaCl, in excess of 90% of cell surface-bound Ang II was dissociated from control, NO2-, and phospholipase B-exposed cells, and there was less than 2% of Ang II detectable when acid-treated cells were subjected to NaOH solubilization. In cells exposed to phospholipase A2, acetic acid treatment did not release cell-bound Ang II, and the remaining Ang II was recovered in the NaOH solubilized fraction.(ABSTRACT TRUNCATED AT 250 WORDS)