atrial-natriuretic-factor and Kidney-Papillary-Necrosis

The renal responses to acute expansion of the blood volume (20%), acute saline loading (5% body wt), or administration of atrial natriuretic peptide (ANP) were investigated in rats 7-10 days after inducing experimental renal papillary necrosis by the injection of bromoethylamine hydrobromide. In normal rats, urinary Na output (UNaV) increased from 1 +/- 0.4 to 16.6 +/- 1.7 mumol/min. In rats with papillary necrosis, UNaV only increased from 1.1 +/- 0.2 to 2.5 +/- 0.5 mumol/min. In contrast, the natriuretic responses to saline loading in normal rats (from 1.7 +/- 0.2 to 21.6 +/- 2.4 mumol/min) and to the infusion of ANP (from 0.8 +/- 0.1 to 7.6 +/- 0.8 mumol/min) were not significantly attenuated in rats with papillary necrosis. The absence of a natriuretic response to hypervolemia in rats with papillary necrosis was not a result of failure to secrete ANP, because plasma levels of immunoreactive ANP increased three- to four-fold in rats with papillary necrosis and in untreated rats. It is concluded that the mechanisms mediating the natriuretic and diuretic responses to acute expansion of the blood volume mainly involve alterations in inner medullary function. In contrast, natriuretic responses to saline loading and pharmacological doses of ANP are apparently mediated by more superficial cortical nephrons.

Topics: Animals; Atrial Natriuretic Factor; Blood Pressure; Blood Volume; Ethylamines; Glomerular Filtration Rate; Kidney Papillary Necrosis; Male; Natriuresis; Rats; Rats, Inbred Strains; Reference Values; Sodium Chloride

This study compared the effects of atriopeptin III (AP III) on sodium excretion and renal interstitial hydrostatic pressure (RIHP) in control rats and in rats pretreated with 2-bromoethylamine (BEA) to produce papillary necrosis. In control rats, infusion of AP III (100 ng.kg-1.min-1) increased sodium excretion from 2.2 +/- 0.7 to 6.4 +/- 0.9 microeq.min-1.g kidney wt-1 and RIHP from 6.8 +/- 0.7 to 8.7 +/- 0.9 mmHg, whereas glomerular filtration rate and renal blood flow were unaltered. Similar results were obtained in rats pretreated with BEA 48 h before the experiment. In rats studied 6 wk after BEA treatment, the papilla was absent and there was atrophy of juxtamedullary nephrons. AP III did not alter sodium excretion or RIHP in this group of rats. These results indicate that 1) an intact renal papilla and/or juxtamedullary nephron population may be required for the natriuretic effect of AP III; 2) the papillary injury 48 h after BEA is not sufficient to abolish the natriuretic response to AP III; and 3) elevations in RIHP may play a role in the natriuretic response to AP III.

Topics: Acetazolamide; Animals; Atrial Natriuretic Factor; Ethylamines; Furosemide; Hemodynamics; Kidney Cortex; Kidney Medulla; Kidney Papillary Necrosis; Male; Natriuresis; Rats; Rats, Inbred Strains

The current study was designed to evaluate whether the renal papilla participates in the natriuretic and diuretic response to atrial natriuretic factor (ANF). Papillary necrosis was induced in female rats by intravenous infusion of 2-bromoethylamine hydrobromide (BEA) 48 h prior to clearance experiments; untreated (UNT) animals served as controls. Rats were anesthetized with pentobarbital sodium, tracheotomized, and catheters placed in a femoral artery and vein and in the bladder. At the time of surgery, the bladder urine was collected and its osmolality used as an indication of papillary destruction. Mean urine osmolalities (+/- SE) of BEA rats were significantly lower than those of UNT rats (443 +/- 10 vs. 1,229 +/- 57 mosmol/kg, respectively), indicating that BEA caused papillary necrosis. Synthetic ANF (rat 8-33) was given as a bolus intravenously (1.25, 2.5, 5.0 micrograms/kg). The ANF-induced increases in sodium excretion were not significantly different between UNT and BEA rats at any ANF dose. These results demonstrate that a functional papilla is not required for the action of ANF in the rat.

Topics: Animals; Atrial Natriuretic Factor; Ethylamines; Female; Glomerular Filtration Rate; Kidney; Kidney Papillary Necrosis; Natriuresis; Osmolar Concentration; Potassium; Rats; Rats, Inbred Strains