The effect of a decrease in arterial blood pressure on renal urodilatin excretion in anesthetized rats

Background

We have recently shown that the renal excretion of urodilatin (U_UROV) can be modified by renal perfusion pressure in vitro[1]. It is not clear whether an interaction between arterial blood pressure and U_UROV may also be observed in vivo.

Methods

Anesthetized male Sprague–Dawley rats were studied for 180 min. Measurements were performed every 30 min. We determined mean arterial pressure (MAP), urine flow (UV), glomerular filtration rate (GFR), the renal excretion of sodium (U_NaV), and of urodilatin (U_UROV; determ ined by RIA). Rats were randomly assigned to a control group (CON: n = 10) and a hypotension group (HYP: n = 10). After 60 min stabilization (baseline [BL]), in the HYP group, blood pressure was decreased 30 mmHg below individual BL levels for 60 min by a continuous infusion of sodium nitroprusside (intervention [IV]). Thereafter, rats were allowed to recover for another 60 min (recovery [RC]). Data were averaged for the respective study periods; renal function parameters and U_UROV are given as relative values in comparison with the BL period.

Results

In the HYP group, the decrease in MAP during the IV period was accompanied by decreased UV (CON: 216.8 ± 36.9%; HYP: 89.3 ± 11.1%; P = 0.04). U_NaV (CON: 267.2 ± 74.9%; HYP: 70.9 ± 12.6%; P = 0.018), and U_UROV (CON: 178.4 ± 40.5%; HYP: 70.9 ± 12.6%; P = 0.01). GFR during the IV period was not different between both groups.

Conclusions

These data further support a role of arterial blood pressure in the regulation of the renal excretion of urodilatin.