Role of renal medullary inducible nitric oxide synthase in the regulation of arterial pressure.

In the present work, we have examined the effects of selective inhibition of the inducible isoform of nitric oxide synthase (iNOS) in rat medulla by aminoguanidine (AG) on the arterial pressure of Dahl salt sensitive (DS), Dahl salt-resistant (DR) and Sprague Dawley (SD) rats by chronic in vivo hemodynamic experiment, the effect of sodium chloride (NaCl) or NaCl plus AG infusion on urinary nitrate/nitrite (urinary NO3/NO2 UNO(x)), the end product of nitric oxide (NO), excretion, glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and plasma renin activity (PRA). Furthermore, an iNOS activity assay was also made. The results showed that AG infusion significantly augmented the pressor response of DS and SD rats to high NaCl (8%) intake, and decreased GFR, ERPF and PRA of DS rats. In addition, in DS rats, renal medullary interstitial administration of high NaCl significantly elevated the iNOS activity of renal tissue, especially inner medulla and outer medulla, and greatly increased UNO(x) excretion. Therefore, it is concluded that inducible NOS is an important modulator of blood pressure in case of NaCl-induced hypertension.