The role of
nitric oxide (NO) and
prostaglandins (PG) in modifying renal hemodynamics was examined in clipped and nonclipped kidneys of unilateral
renal artery stenosis. Chronic unilateral renal
ischemia was established by 4-wk-clipping the left renal artery of canine kidneys, and renal interstitial nitrate+nitrite and
PGE(2) contents were evaluated by the microdialysis technique. Unilateral
renal artery stenosis caused 45 +/- 1 and 73 +/- 1% decrements in renal plasma flow (RPF) in moderately and severely clipped kidneys and 21 +/- 3% decrements in nonclipped kidneys with severe
stenosis. Renal nitrate+nitrite decreased in moderately (-31 +/- 1%) and severely clipped kidneys (-63 +/- 4%).
N(omega)-nitro-L-arginine methyl ester reduced RPF (-56 +/- 3%) and glomerular filtration rate (GFR; -54 +/- 3%) in moderately clipped kidneys, whereas this inhibitory effect was abolished in severely clipped kidneys. In contrast, renal
PGE(2) contents increased modestly in moderate clipping and were markedly elevated in severely clipped kidneys (from 111 +/- 7 to 377 +/- 22 pg/ml);
sulpyrine impaired renal hemodynamics only in severely clipped kidneys. In contralateral nonclipped kidneys, although renal
PGE(2) was not increased,
sulpyrine reduced RPF (-32 +/- 1%) and GFR (-33 +/- 3%) in severe
stenosis. Collectively, NO plays a substantial role in maintaining renal hemodynamics both under basal condition and in moderate
renal artery stenosis, whereas the contributory role shifts from NO to PG as
renal artery stenosis progresses. Furthermore, because intrarenal
angiotensin II is reported to increase in nonclipped kidneys, unilateral severe
ischemia may render the nonclipped kidney susceptible to PG inhibition.