ANG-II STIMULATES ENDOTHELIAL NITRIC-OXIDE SYNTHASE EXPRESSION IN BOVINE PULMONARY-ARTERY ENDOTHELIUM

Although angiotensin II (ANG II) is a known pulmonary vasoconstrictor, the purpose of this study was to examine the effect of ANG II on pulm onary artery endothelial cell nitric oxide synthase (ecNOS) mRNA and p rotein expression. Cultured bovine pulmonary artery endothelial (BPAE; passages 5-8) cells were incubated for 0-12 h with 10(-6) M ANG II. T otal RNA was extracted, and ecNOS expression was assessed by Northern blot analysis. In BPAE cells, ecNOS mRNA was significantly increased 2 .4 +/- 0.3-fold (P < 0.05 vs. basal; n = 5) 6 h after the addition of ANG II over basal levels. In a similar time course, it was found that ecNOS protein concentrations are increased 247 +/- 62% (P < 0.05 vs. b asal; n = 8) over basal levels 4 h after ANG II addition. There is a s econd protein peak 8 h after ANG II addition in which ecNOS was increa sed 333 +/- 145% over basal (P < 0.05, n = 3). These data suggest that ANG II stimulates ecNOS mRNA expression and are followed by increased levels of ecNOS protein in cultured BPAE cells, consistent with an ob served increase in nitrite production. Both the increase in ecNOS prot ein and mRNA expression could be inhibited with the ANG II receptor an tagonist saralasin. Additionally, actinomycin D, an inhibitor of trans cription, prevented the rise in mRNA at 6 h while cycloheximide inhibi ted the initial protein peak. The effects of ANG II on ecNOS were spec ific for the pulmonary artery endothelium. Addition of ANG II did not increase ecNOS protein or mRNA expression in parallel studies in bovin e coronary artery endothelium. The stimulation of ecNOS by ANG II may act to protect the lung and maintain low pulmonary artery pressures in the renin-agiotensin model of systemic hypertension.