Effect of thromboxane and nitric oxide blockade on renal blood flow increase during volume expansion in hydronephrotic rats

Objectitve: It has recently been found that hydronephrotic rats, despite lo w diuresis, show a significant increase in renal blood flow (RBF) during vo lume expansion. The present experiments were designed to evaluate the mecha nisms underlying this phenomenon. Material and methods: Three-week-old Sprague-Dawley rats underwent partial obstruction of the left using the Ulm-Miller psoas groove technique. The ef fects on RBF were studied 3 weeks later under general anesthesia using real -time ultrasound flowmetry, first during normohydration and then during ext racellular volume expansion, in both untreated animals, and after prior blo ckade of either thromboxane or nitric oxide. Results: Significant hydronephrosis developed in all cases. RBF was normal under control conditions. During volume expansion RBF increased significant ly in untreated experimental animals (mean 7.5%). In contrast to this findi ng, RBF remained unchanged during volume expansion in both the thromboxane and nitric oxide blockade groups. Conclusion: It is concluded that a thromboxane- and/or nitric oxide-depende nt RBF redistribution takes place in hydronephrotic kidneys during volume e xpansion.