The recovery of renal function in rats after release of unilateral ureteral obstruction: the effects of moderate isotonic saline loading.

Following 24 h of ureteral obstruction in the rat, renal blood flow and glomerular filtration rate are markedly depressed. The effect of saline loading on post-obstructive glomerular filtration (GFR) was studied in 15 female Sprague-Dawley rats in the awake state, 4 h following the release of 24 h of unilateral ureteral obstruction. Group I (n = 8) received 39 microliters min-1 of 0.9% saline only for 1 h prior to study and Group II (n = 7) received 78 microliters min-1 of 0.9% saline for the whole 4 h prior to study. The Cin and CPAH of the post-obstructed kidney were significantly reduced over control values in both groups. Saline loading (Group II) resulted in an improvement in Cin in the post-obstructed kidney compared with group I (3.22 +/- 0.14 vs. 2.19 +/- 0.14 ml/min/kg BW, P less than 0.001). This was independent of any change in CPAH. In two further groups of rats the saline loading protocol was shown to cause a rise in the excretion of urinary cGMP in the post-obstructed kidney, but not the contralateral control kidney. In addition, administration of exogenous atriopeptin (1-24) to non-saline loaded animals resulted in a qualitatively similar alteration in renal function to saline loading, namely a rise in Cin and an increase in excretion of cGMP by the post-obstructed kidney, and no change in CPAH.(ABSTRACT TRUNCATED AT 250 WORDS)