Interactions between nitric oxide and prostanoids in isolated perfused kidneys of the rat

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Abstract
1 The present study was aimed to assess the interaction between nitric oxide (NO) and thromboxane (Tx) A2-prostaglandin (PG) H2 in single-pass perfused isolated kidneys of the rat. 2 Noradrenaline (NA, 63 and 110 nM) dose-dependently elevated the renal vascular resistance (RVR), the glomerular filtration rate (GFR) and the urinary excretion of sodium (UNaV). Infusion of Nγ-nitro-L-arginine methyl ester (L-NAME, 100 μm), an inhibitor of NO synthesis, enhanced the effects of NA on RVR and on UNaV, but decreased those on GFR. The TxA2-PGH2 (TP) receptor blockade by GR32191B (10 μm) attenuated this potentiating effect of L-NAME. 3 When renal perfusion pressure was stepwise increased from 90 to 150 mmHg, L-NAME similarly decreased renal perfusion flow rate and GFR. 4 The venous excretion of TxB2 and 6-keto-PGF1α was increased by L-NAME in baseline conditions as well as after NA or increasing renal perfusion pressure (RPP). 5 These results suggest that: (1) TxA2 and PGH2 play an important role in the overall effect of the renal prostanoids, (2) NO strongly interacts with the cyclo-oxygenase pathway and reduces the prostanoid synthesis in the kidney, and (3) the pressor effect of L-NAME partly relies upon the vasoconstrictor effect of TxA2 and PGH2.