Abnormal renal vasodilation to an amino acid infusion in congestive heart failure: normalization by enalapril

Nitrendipine and amlodipine mimic the acute effects of enalapril on renal haemodynamics and reduce glomerular hyperfiltration in patients with chronic kidney disease

Antihypertensive drugs may have an important effect on glomerular haemodynamics. In chronic nephropathy patients, we compared the effect on glomerular haemodynamics of two second-generation dihydropyridinic agents, nitrendipine and amlodipine, with a first generation dihydropyridinic agent and an ACE-inhibitor, enalapril. In all, 32 patients (pts), divided into four groups, received the different drugs: ENA (enalapril, eight pts), NIF (nifedipine, eight pts), NIT (nitrendipine, eight pts) AML (amlodipine, eight pts). The study assessed the effect on glomerular haemodynamics of a single administration of the test drug in baseline conditions and in glomerular hyperfiltration experimentally induced by amino-acid infusion. The glomerular filtration rate (GFR, measured by inulin clearance), effective renal plasma flow (ERPF, measured by p-aminohippurate clearance), renal vascular resistances (RVR) and filtration fraction (FF) were assessed. Administration of AML and NIT test dose reduced FF, as did ENA, but not NIF, in both baseline (AML: P=0.005; NIT: P=0.02; ENA: P=0.007) and glomerular hyperfiltration conditions (AML: P=0.0003; NIT: P=0.03; ENA: P=0.00006). In baseline conditions, only ENA resulted in a significant drop in the GFR (P=0.008), while NIF, NIT and AML induced a significant increase (P=0.003, 0.03, 0.0001, respectively). However, in hyperfiltration conditions, NIT (0.08) and AML (0.00003) caused a decrease in the GFR, as did ENA (0.0003) but not NIF. In all the experimental conditions, a RVR reduction and an ERPF increase were observed. Single dose of NIT and AML were effective in attenuating the effect of amino-acid infusion on glomerular filtration, similar to ENA; this effect of NIT and AML on the glomerular filtration rate is not observed under basal conditions.

Renal implications of the renin-angiotensin-aldosterone system blockade in heart failure

The renin-angiotensin-aldosterone system actively participates in the derangement of renal function since the early stages of heart failure (HF). A diminished capacity to excrete sodium secondary to increased proximal tubular re-absorption and loss of the renal functional reserve are the two most relevant initial alterations of renal function in which angiotensin II has been proven to act directly. Meanwhile, the octapeptide contributes to maintain glomerular filtration rate (GFR) within normal limits through efferent arteriole vasoconstriction. Administration of angiotensin converting enzyme inhibitors (ACEi) or angiotensin receptor antagonists (ARA) may thus be accompanied by a functional fall in that parameter. Advanced age, higher initial serum creatinine, history of hypertension, diabetes and atrial fibrillation predict the onset of GFR impairment associated with blockade of the renin-angiotensin system. Concomitant administration of betablockers may help to protect renal function, and preliminary data indicate that the combination of ACEi and ARA is not accompanied by a higher renal risk. The good prognostic effects of aldosterone antagonists in HF does not seem to be related to intrarenal effects of these compounds with the exception of preventing potassium loss and hypokalemia. The systematic therapeutic use of drug(s) provided with beneficial renal effects, to treat arterial hypertension or myocardial ischemia, may contribute to delay of, or prevent the development of HF.