Failure of atrial natriuretic peptide to induce natriuresis in aortocaval fistula dogs.

Creation of an aortocaval fistula (ACF) in dogs induces salt and water retention, activation of the renin-angiotensin and adrenergic nervous systems and renal papillary ischemia associated with high levels of circulating atrial natriuretic peptide (ANP). The effects of intrarenal ANP (1.2 micrograms/min) infusion on systemic and renal hemodynamics, renal excretory function, renal output of renin and norepinephrine (NE) and papillary plasma flow (PPF) were studied in both normal and ACF dogs. ANP did not alter systemic hemodynamics in either group, but led to a significant increase in renal blood flow (RBF), glomerular filtration rate (GFR), urine flow rate (V), sodium excretion (UNaV) and fractional excretion of sodium (FENa), and a significant decrease in renal vascular resistance (RVR) and urine osmolality (UOsm) in normal dogs. GFR, RBF, RVR, V, UNaV, FENa and UOsm remained unchanged, however, in ACF dogs. In ACF dogs, both renal renin and NE output were significantly greater during baseline and remained significantly greater following ANP infusion, associated with a significantly lower PPF compared with normal dogs. These data suggest that ACF dogs are resistant to the renal effects of ANP, which can neither mitigate the hormonal mediators of sodium retention nor reverse the papillary ischemia observed in this model.