Studies conducted by numerous research laboratories, including ours, underscore the need for undertaking cardiorenal approaches to effectively contain the progression of certain cardiovascular diseases. Edema is the hallmark of congestive heart failure (HF). The most important causes of edema in HF are salt and water retention by the kidneys. The potential causes of altered renal handling of salt and water may involve a decrease in glomerular filtration rate, an increase in tubular reabsorption of sodium or both. We have previously demonstrated that the enzyme dipeptidyl peptidase IV ( DPPIV) physically associates with the Na+/ H+ exchanger isoform 3 (NHE3) in the renal proximal tubule and that DPPIV inhibitors inhibit the transport activity of this transporter. Additionally, we have demonstrated that the peptide glucagon-like - 1 (GLP- 1) , a well-known substrate of DPPIV, which has natriuretic and vasodilatory actions, upon binding to its receptor GLP-1R, activates the cAMP/PKA signaling cascade and consequently inhibits NHE3 activity in renal proximal tubule. Furthermore, GLP-1 increases glomerular filtration rate and renal plasma flow in healthy rats. In the present study, we will test the hypothesis that administration of the DPPIV inhibitor (vildagliptin) restores renal handling of salt and water in rats with congestive HF. More specifically, we will investigate whether: ( i ) the administration of the vildagliptin reduces pulmonary congestion , (ii ) normalizes glomerular filtration rate , increases the levels of phosphorylation of serine 552, a consensus site for PKA located in the tail C -terminal NHE3 in the renal cortex, and reduces the activity of this transporter in rats with established HF.
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