Renal effects of neutral endopeptidase inhibition in euvolemic and hypervolemic rats

Candoxatrilat is a potent and selective inhibitor of neutral endopeptidase (EC 3.4.24.11), the enzyme responsible for the degradation of atrial natriuretic factor (ANF). In these studies, the renal effects of candoxatrilat were investigated in euvolemic and hypervolemic anaesthetised rats. In euvolemic rats, candoxatrilat (675 micrograms/kg per h) had no effect on urine output, sodium and potassium excretion or urinary cyclic GMP excretion. However, in hypervolemic rats, the natriuretic and diuretic responses to volume expansion were markedly potentiated by the candoxatrilat infusion, with a concomitant increase in urinary cyclic GMP. Acute volume expansion was characterised by natriuresis, diuresis and increased levels of plasma ANF and cyclic GMP (1.5-fold and 2-fold increases respectively, when compared to euvolemic rats). The results presented suggest that plasma ANF levels and volume status modulate responses to neutral endopeptidase inhibition. The development of the neutral endopeptidase inhibitor, candoxatrilat, provides the opportunity to exploit endogenous ANF effectively in disease states with elevated ANF.