Background
Treatment with urodilatin (URO; ANP-95-126), a kidney derived natriuretic peptide, may be beneficial in patients with incipient acute renal failure after cardiac surgery [1]. The findings about mechanisms regulating endogenous production and renal excretion of URO are controversial. Recent evidence suggests that urinary excretion of urodilatin (VUROU) is increased in patients after uncomplicated cardiac surgery and positively correlated with blood pressure [2].
Objective
To determine the effects of different perfusion pressures on urine flow (VU), urinary excretion of sodium (VNaU), potassium (VkU) and urodilatin (VUROU) and the concentration of urodilatin in the perfusate (PURO) in isolated perfused rat kidneys.
Materials and methods
Kidneys from Sprague-Dawley rats were perfused for 180 min with constant perfusion pressures (80 mmHg (n = 4); 120 mmHg (n = 4)) in a closed circuit system. Samples were taken every 30 min. The concentration of urodilatin in urine and perfusate were determined by a radioimmuno-assay for raturodilatin (rURO: Immundiagnostik, Bensheim, Germany) not cross-reacting with rBNP, rCNP, rCDD/ANP-99-126 or hURO.
Results
Mean VU, VNaU, VkU and VUROU were significantly higher with a perfusion pressure of 120 mmHg than with 80 mmHg (all: P < 0.05); PURO did not change significantly.
Conclusion
Our data suggest that renal perfusion pressure and consequently mean arterial blood pressure are determinants of VUROU. Additionally, our data underline the importance of perfusion pressure for adequate renal function; this may be especially relevant for patients at risk to develop acute renal failure after cardiac surgery.
References
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