Comparison of the effects of calcium antagonists and converting enzyme inhibitors on renal function under normal and hypertensive conditions

Year-long antihypertensive therapy with candesartan completely prevents development of cardiovascular organ injuries in spontaneously hypertensive rats

Most previous studies have examined the effects of antihypertensive drugs in hypertensive animals for only a few months, and little information has been provided as to the protective effects of lifetime antihypertensive medication against cardiovascular organ injury. In this study, spontaneously hypertensive rats (SHR) were treated for 1 year with an angiotensin-II receptor antagonist (ARB) and the development of hypertensive organ injury was evaluated. Male 15-week-old SHR (n = 9) were given 25 mg/L candesartan (CS) in their drinking water for 1 year. Twelve SHR and 9 normotensive Wistar-Kyoto rats (WKY) were given normal tap water. Tail-cuff blood pressure was almost normalized by CS throughout 1 year (at 12-months: WKY 132 ± 3, SHR 229 ± 3, CS 137 ± 4 mmHg). After 1 year, cardiac ventricular weight (SHR +33%, CS -2% versus WKY) and aortic thickness (SHR +34%, CS +4% versus WKY) in the CS-treated SHR rats were not different than those of WKY. Echocardiographic midwall fractional shortening (SHR -18%, CS -1% versus WKY) and left ventricular hydroxyproline content (SHR +47%, CS +11% versus WKY) were also improved by CS to the WKY level. With respect to kidney function, GFR (SHR -24%, CS +9% versus WKY) was preserved, proteinuria (SHR +312%, CS +12% versus WKY) was reduced, and the histological glomerular injury rate (SHR +186%, CS +6% versus WKY) was reduced by CS. These results suggest that long-term antihypertensive therapy with CS can completely prevent hypertensive cardiovascular and renal injuries in SHR.

Are differences in calcium antagonists relevant across all stages of nephropathy or only proteinuric nephropathy?

PURPOSE OF REVIEW

The main effects of classic calcium antagonists are mediated by the inhibition of L-type calcium channels broadly distributed within the renal vascular bed. Calcium antagonists act predominantly on the afferent arterioles, and dihydropyridines can favour the increase in glomerular hypertension and progression of kidney diseases, in particular when systemic blood pressure remains uncontrolled.

RECENT FINDINGS

Calcium antagonists have been widely used in clinical practice because of their antihypertensive capacity. The prevention of renal damage is a very important aim of antihypertensive therapy. This is particularly so taking into account the high prevalence of chronic kidney disease in the general population. Non-dihydropyridines such as verapamil have been shown to possess an antiproteinuric effect that could be particularly relevant.

SUMMARY

Recent data from clinical trials have confirmed that, in hypertensive patients with preserved renal function or with chronic kidney disease, calcium antagonists are effective antihypertensive drugs to be considered alone or in combination with an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. In those patients presenting with proteinuric kidney disease, non-dihydropyridines could reduce proteinuria to a greater degree than dihydropyridines.

Benazepril slows progression of renal dysfunction in patients with non-diabetic renal disease

AIM

The present study examined the effects of benazepril, an angiotensin-converting enzyme inhibitor, on the progression of renal insufficiency in patients with non-diabetic renal disease.

METHODS

Fifteen patients with non-diabetic renal disease whose serum creatinine (Cr) ranged from 1.5 to 3.0 mg/dL were given either benazepril (2.5-5 mg) or placebo once daily for 1 year in a random crossover manner. In both periods, antihypertensive medications were increased if blood pressure was greater than 130/85 mmHg. Blood sampling and urinalysis were performed bimonthly throughout the study period.

RESULTS

Blood pressure was similar when comparing the benazepril and the placebo periods (128+/-12/83+/-6 vs 129+/-10/83+/-7 mmHg). Serum Cr significantly increased from 1.62+/-0.18 to 1.72+/-0.30 mg/dL (P=0.036) during the placebo period, while there was no statistically significant increase in serum Cr during the benazepril period (from 1.67+/-0.17 to 1.71+/-0.27 mg/dL). The slope of decrease of the reciprocal of serum Cr was steeper in the placebo period than in the benazepril period (-0.073+/-0.067 vs-0.025+/-0.096/year, P=0.014). Urinary protein excretion was lower during the benazepril period than during the placebo period (0.57+/-0.60 vs 1.00+/-0.85 g/gCr, P=0.006). Serum K was significantly higher in the benazepril period than in the placebo period (4.4+/-0.5 vs 4.2+/-0.5 mEq/L, P<0.001), but no patient discontinued benazepril therapy as a result of hyperkalemia.

CONCLUSION

Long-term benazepril treatment decreased the progression of renal dysfunction in patients with non-diabetic renal disease by a mechanism that is independent of blood pressure reduction.

Effects of valsartan on the progression of chronic renal insufficiency in patients with nondiabetic renal diseases

The present study tested the effects of valsartan, an angiotensin II receptor blocker, on the progression of renal insufficiency in patients with nondiabetic renal diseases. The study subjects were 22 patients with nondiabetic renal diseases whose serum creatinine (Cr) ranged from 1.5 to 3.0 mg/dl. Valsartan (40-80 mg) or placebo was given once daily for 1 year each in a random crossover manner. In both periods, antihypertensive medications were titrated when the blood pressure was not lower than 140/90 mmHg. Blood sampling and urinalysis were performed bimonthly throughout the study periods. The average blood pressure was comparable between the valsartan and the placebo periods (130 +/- 9/86 +/- 6 vs. 131 +/- 8/86 +/- 6 mmHg). Serum Cr significantly increased from 1.9 +/- 0.5 to 2.3 +/- 0.8 mg/dl (p < 0.001) during the placebo period, but the change was insignificant in the valsartan period (2.1 +/- 0.6 to 2.2 +/- 0.9 mg/dl). The slope of decrease in the reciprocal of serum Cr was steeper in the placebo period than in the valsartan period (-0.064 +/- 0.070/year vs. -0.005 +/- 0.050/year, p < 0.01). During the valsartan period, urinary protein excretion was less than that during the placebo period (0.75 +/- 0.73 vs. 1.24 +/- 0.92 g/g Cr, p < 0.001). Serum K was significantly higher in the valsartan period than in the placebo period (4.6 +/- 0.5 vs. 4.4 +/- 0.5 mEq/l, p < 0.05); however, no patients discontinued taking valsartan as a result of hyperkalemia. It is possible that long-term treatment with an angiotensin II receptor blocker, valsartan, is effective at retarding the deterioration of renal function in patients with nondiabetic renal disease by a mechanism independent of blood pressure reduction.

Effects of nifedipine, verapamil and diltiazem on serum biochemical parameters and aortic composition of atherosclerotic chickens

Calcium appears to be involved in many of the cellular events, which are thought to be important in atherogenesis. In this study, we examine the effects of three calcium entry blockers (nifedipine, verapamil, and diltiazem at clinical and higher doses) on serum biochemical parameters and aortic calcium, cholesterol and triglyceride concentrations of atherosclerotic egg-fed chickens. All egg-fed chickens (treated and non-treated) showed an increase in serum total cholesterol, LDL-cholesterol and triglycerides without significant effect when calcium entry blockers were used. Increased HDL values were observed in clinical and high-dose nifedipine and clinical dose verapamil groups. The high-dose diltiazem group presented increased zinc values with respect to the clinical dose diltiazem and control groups. The sodium concentrations were significantly decreased in all the groups of animals treated with calcium entry blockers at high-doses and nifedipine at clinical doses. Measurements of aortic calcium concentration showed a significant decrease in the high-dose nifedipine and verapamil groups. Calcium channel blockers had a tendency to decrease total cholesterol in aortas. The values were statistically significant for the high-dose verapamil, and nifedipine groups. Only nifedipine showed a significant decrease for this parameter at clinical dosages. Triglyceride concentrations in aortas were significantly low in animals fed an atherogenic diet and treated with calcium channel blockers, without differences between drugs or dosages used in the experiment. In addition, the chicken atherosclerosis model has proved itself useful and very suitable for in vivo drug intervention studies.

The J-curve in hypertension

The J-curve debate has continued for 25 years. Dependency upon observational and retrospective studies has confused the issue; only the full publication of data from the prospective, randomized Hypertension Optimal Treatment (HOT) study has thrown genuine light on the problem. Many examples of the J-curve relationship between blood pressure and cardiovascular/noncardiovascular events are due to reverse causality, where underlying disease (eg, poor left ventricular function, poor general health, poorly compliant/stiff arteries) is the cause of both the low blood pressure and the increased risk of both cardiovascular and noncardiovascular events. The J-curve in patients with stiff arteries (wide pulse pressure) may be exacerbated by treatment. From the full publication of the HOT study database it is now reasonable to conclude that for nonischemic hypertensive subjects the therapeutic lowering of diastolic blood pressure (DBP) to the low 80s mm Hg is beneficial, but it is safe (though unproductive) to go lower. However, in the presence of coronary artery disease (limited coronary flow reserve) there is a J-curve relationship between treated DBP and myocardial infarction, but not for stroke. In such high-risk (for myocardial infarction) cases it would be prudent to avoid lowering DBP to below the low 80s mm Hg.

Regression of chronic L -NAME-treatment-induced left ventricular hypertrophy: effect of captopril

Long-term administration of N(G)-nitro- L -arginine methyl ester (L -NAME) induces development of NO-deficient hypertension and left ventricular (LV) hypertrophy. In this work, we examined the effect of spontaneous and captopril-induced recovery on LV hypertrophy and protein composition in rats with developed L -NAME-induced hypertension. Four groups of rats were investigated: control L -NAME 40 mg/kg/day for 4 weeks (L -NAME) L -NAME 40 mg/kg/day for 4 weeks followed by 3-week spontaneous recovery (L -NAME+R) L -NAME 40 mg/kg/day for 4 weeks followed by 3 weeks of captopril treatment at a dose of 100 mg/kg/day (L -NAME+C). LV hypertrophy in the L -NAME group was associated with an increase in content and concentration of left ventricular DNA and RNA, concentration of metabolic proteins (MP) and soluble collagenous proteins (SCP). Spontaneous recovery period reduced the hypertension, without regression of LV hypertrophy. Left ventricular DNA and RNA content were increased in the L -NAME+R group. In this group, concentrations of MP, contractile proteins (CP), and collagenous proteins did not differ from those in the L -NAME group. Captopril treatment caused total regression of hypertension and LV hypertrophy and decreased both content and concentration of DNA and RNA, as well as the contents of MP, CP and SCP v the L -NAME group. However, after captopril treatment, concentration of collagenous and non-collagenous protein fractions remained increased v control. We conclude that spontaneous regression of L -NAME-induced hypertension is not associated with regression of LV hypertrophy. LV hypertrophy was regressed only in captopril-treated animals.

The natriuretic effect of nifedipine gastrointestinal therapeutic system remains despite the presence of mild-to-moderate renal failure

BACKGROUND

Calcium channel blockers facilitate the renal excretion of sodium and this effect is maintained during chronic administration of these drugs. However, it is unknown whether this natriuretic effect remains despite the presence of a decreased renal function.

OBJECTIVE

To compare the natriuretic capacity of nifedipine gastrointestinal therapeutic system (GITS) and lisinopril in patients with mild-to-moderate chronic renal failure.

METHODS

An open-label, randomized, comparative study was conducted to compare the natriuretic capacity of nifedipine GITS and lisinopril in the presence of mild-to-moderate renal failure (creatinine clearance 30-80 ml/min). After a wash-out period of 4 weeks an intravenous saline infusion (30 ml/kg of body weight of isotonic saline in 4 h) was performed and repeated after 4 weeks of active therapy. Two sex- and age-matched groups of hypertensive patients (n = 25) were included in the study. Renal failure was diagnosed as secondary to nephrosclerosis in all the patients.

RESULTS

A significant increase in the renal capacity to excrete the sodium load was observed in patients receiving nifedipine GITS (n = 11) but not in those taking lisinopril (n = 13). Both drugs controlled blood pressure to a similar extent. No changes were observed in body weight, glomerular filtration rate and renal plasma flow (measured as inulin and paraaminohippurate clearances). A significant drop was observed in urinary albumin excretion after lisinopril, but not after nifedipine. Heart rate was higher in nifedipine group.

CONCLUSION

The natriuretic capacity of nifedipine GITS remains despite the presence of mild-to-moderate chronic renal failure. Such an effect takes place in the absence of changes in renal hemodynamics, suggesting that it is caused by a direct tubular effect.

Are renal hemodynamics a key factor in the development and maintenance of arterial hypertension in humans?

The kidney plays a key role in the control of body fluids and blood pressure. Evidence has shown that impairment of renal function can lead to the development of arterial hypertension. The regulation of renal blood flow appears to be a key element in the pathophysiology of the hypertensive process, because multiple evidence suggests the existence of a functional enhancement of renal vascular tone in this disorder. The existence of renal vasoconstriction and of an inherited defect in the regulation of renal blood flow has been proposed in the prehypertensive stage. The mechanisms responsible for this alteration include a lack of modulation of the renal vasculature to angiotensin II, increased sympathetic activity, or suppressed renal dopaminergic activity. Established hypertension is characterized by elevated renal vascular resistance, decreased renal blood flow, sustained glomerular filtration rate, and increased filtration fraction. The increase in renal vascular resistance is initially due to elevations in renal vascular tone and is reversible, whereas later it becomes irreversible because of structural changes involved in nephrosclerosis. Antihypertensive drugs are able to decrease blood pressure and to prevent the development of further renal vascular damage independently of variable effects on renal hemodynamics.

Angiotensin-converting enzyme inhibitors in the treatment of mild arterial hypertension

Angiotensin-converting enzyme inhibitors are nowadays widely employed for the treatment of arterial hypertension. They exhibit comparable levels of efficacy and better tolerability when compared with the other antihypertensive agents. In mild arterial hypertension they have been shown to be more efficacious than nonpharmacological therapy that is recommended as the first-step therapeutic approach for most cases of this type of hypertension. Potential advantages for the control of associated metabolic risk factors and specific renal and cardiac effects make these drugs suitable for the first step pharmacological therapy on mild hypertension.

Renal effects of antihypertensive medications: an overview

A variety of antihypertensive agents are available for management of elevated arterial pressure. Although these agents all effectively lower arterial pressure, they have somewhat diverse renal hemodynamic profiles. This report reviews the various similarities and differences in renal hemodynamic profiles among the different antihypertensive agents.

Current issues in hypertension. Old questions with new answers and new questions

Hypertension is a systemic vascular disease that makes its mark upon the "target organs"--heart, brain, and kidneys--through the hemodynamic hallmark of the disease, a progressively increasing vascular resistance to the forward flow of blood. The effect of pressure overload upon the heart is one of concentric hypertrophy of the left ventricle that is, in turn, associated with an independent risk of morbidity and mortality. Reduction of arterial pressure reverses the risk associated with the elevated arterial pressure and also diminishes the risk from hemorrhagic and thrombotic strokes. Why the risk of the interaction of hypertensive and atherosclerotic diseases can be reduced on the brain but not as impressively on the heart remains to be learned, but certain recent lines of clinical and experimental evidence point to some answers. The issue as to why, in the face of increasing numbers of patients receiving the benefits of therapy, there is an alarming increase in patients with end-stage renal disease defies more imagination and study. Thus, many of the old questions seem to be achieving some meaningful answers; but associated with these new answers we are confronted with new questions.

Comparative pharmacokinetic and clinical profiles of angiotensin-converting enzyme inhibitors and calcium antagonists in systemic hypertension

Angiotensin-converting enzyme (ACE) inhibitors and calcium antagonists are important classes of antihypertensive agents. Within their respective classes, ACE inhibitors and calcium antagonists share common pharmacokinetic properties, but in contrast to ACE inhibitors, some calcium antagonists may cause a significant increase in plasma digoxin concentrations. Clinically, both classes of agents have been shown to be safe and effective in large-scale, long-term clinical trials. ACE inhibitors appear to be very well tolerated and may be associated with fewer adverse effects than some calcium antagonists. ACE inhibitors appear to blunt diuretic-induced hypokalemia, hypercholesterolemia, hyperuricemia, and hyperglycemia. Both classes of agents can be used safely in patients with renal disease, diabetes mellitus, peripheral vascular disease, and chronic obstructive pulmonary disease. They may also be used in the elderly. While ACE inhibitors are particularly useful in hypertension accompanied by congestive heart failure, calcium antagonists can be very useful when angina pectoris is present in the hypertensive patient.

ACE inhibitors in renal disease

Recent experimental studies suggest that the resistance state of the preglomerular and postglomerular capillary arterioles may determine if a particular class of antihypertensive agents will protect the kidney from hemodynamically mediated glomerular injury. This review discusses (1) the effects of angiotensin II on the renal microcirculation, (2) the pathophysiology of essential hypertensive renal disease, (3) the renal pharmacology of angiotensin-converting enzyme (ACE) inhibitors, and (4) the hypothesis that renal protection is dependent on control of systemic and glomerular hypertension.

Renal effects of calcium entry blockers

Calcium entry blockers exert several characteristic effects on renal function that contribute to their blood-pressure lowering capacity. They are able to dilate renal vasculature and, in certain circumstances, can increase the glomerular filtration rate, both effects being dependent on the preexisting vascular tone. Calcium blockers are also able to increase renal sodium excretion, mainly through a direct tubular effect that remains during the chronic administration of these drugs. These effects clearly differentiate calcium entry blockers from nonspecific vasodilators and contribute to their effectiveness when they are used as first-step drugs in the therapy of arterial hypertension.