American journal of physiology. Renal physiology
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Am. J. Physiol. Renal Physiol. · Feb 2002
Losartan treatment normalizes renal sodium and water handling in rats with mild congestive heart failure.
This study was designed to examine the effect of losartan treatment on renal tubular function in rats with mild congestive heart failure (CHF) induced by ligation of the left anterior descending artery. In rats with CHF, there was a significant decrease in daily sodium excretion, which caused sodium retention relative to control rats. Renal function studies revealed that glomerular filtration rate and proximal tubular sodium handling were normal. ⋯ Losartan treatment normalized expression of NKCC2 and decreased expression of the vasopressin-regulated water channel aquaporin-2. This was associated with normalization of daily sodium excretion and normalization of the aquaretic response to V(2)-receptor blockade. Together, these results indicate that, in rats with CHF, losartan treatment inhibits increased sodium reabsorption through NKCC2 in the thick ascending limb of Henle's loop and water reabsorption through aquaporin-2 in the collecting ducts, which may be involved in improving renal function in losartan-treated CHF rats.
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Am. J. Physiol. Renal Physiol. · Feb 2002
Blood flow-dependent changes in renal interstitial guanosine 3',5'-cyclic monophosphate in rabbits.
We examined responses of renal interstitial guanosine 3',5'-cyclic monophosphate (cGMP) to changes in renal perfusion pressure (RPP) within and below the range of renal blood flow (RBF) autoregulation. A microdialysis method was used to monitor renal cortical and medullary interstitial cGMP levels in anesthetized rabbits. RPP was reduced in two steps: from ambient pressure (89 +/- 3 mmHg) to 70 +/- 2 mmHg (step 1) and then to 48 +/- 3 mmHg (step 2). ⋯ During L-NAME treatment, renal interstitial concentrations of cGMP in the cortex and medulla were similarly not altered in step 1. However, L-NAME significantly attenuated cGMP responses to a reduction in RPP in step 2. These results indicate that acute changes in RBF result in alterations in nitric oxide-dependent renal interstitial cGMP levels, with differential effects in the medulla compared with the cortex.