Urinary excretion of urodilatin is increased during pressure natriuresis in the isolated perfused rat kidney

The findings about mechanisms regulating production and excretion of urodil atin [ANP-(95-126)], a member of the atrial natriuretic peptide (ANP) famil y, are controversial. To elucidate a possible relationship between arterial blood pressure and renal urodilatin excretion, we studied the effects of d ifferent perfusion pressures on urine flow (UV), urinary sodium (UNaV), uri nary potassium (UKV), and urodilatin excretion (UUROV), and the concentrati on of urodilatin in the perfusate (P-URO) of isolated perfused rat kidneys. Kidneys were perfused for 180 min with constant perfusion pressures (80 an d 120 mmHg, respectively; each, n = 4) in a closed circuit system. Samples of urine and perfusate were taken every 30 min. Mean UV, UNaV, UKV, and UUR OV values were significantly higher with a perfusion pressure of 120 mmHg t han with 80 mmHg, whereas P-URO did not change significantly. Serial measur ements revealed no direct relation of UUROV with either UNaV or UV. This su ggests that renal perfusion pressure is a determinant of UUROV and that uri nary and venous effluent concentrations of urodilatin (probably production) are not coupled directly and that UUROV and UNaV may dissociate during acu te variations of sodium excretion and UV.