Strategies in antihypertensive therapy: implications of the kidney

Differential effects of antihypertensive drugs on neurohormonal activation: insights from a population-based sample

OBJECTIVES

The clinical course of hypertension or heart failure may be modified by the extent of concurrent neurohormonal activation. Factors that regulate neurohormones in patients with these conditions are complex. In the present study, we examined the relative contribution of antihypertensive therapy to the variability of neurohormonal levels in a well defined population based sample.

DESIGN AND SETTING

Cross-sectional study of a mixed urban and rural population.

SUBJECTS

Middle-aged individuals (n = 646) were analysed in order to elucidate determinants of neurohormone levels by uni- and multivariate comparisons. The assessment included anthropometric, echocardiographic and, if appropriate, genotype information.

RESULTS

The intake of antihypertensive drugs was related to significant alterations of neurohormone levels that, in part, exceeded the contribution of all other variables studied. Multivariate analyses revealed that renin levels were independently related to the intake of beta blockers (n = 80; -8.4 mU L-1; P = 0.001), angiotensin-converting enzyme (ACE)-inhibitors (n = 39; +15.9 mU L-1; P = 0.0001), diuretics (n = 62; +14.3 mU L-1; P = 0.0001), and calcium channel blockers (n = 45; +5.9 mU L-1; P = 0.05). Aldosterone levels were related to ACE-inhibition (-156.5 pmol L-1; P = 0.04) and diuretic treatment (+422.4 pmol L-1; P = 0.0001) in an opposite fashion whereas beta blockers and calcium channel blockers had no significant independent effects. The levels of the atrial natriuretic peptide were significantly related to the use of beta blockers (+3.9 pmol L-1; P = 0.002) and calcium channel blockers (+3.1 pmol L-1; P = 0.05). Finally, serum angiotensinogen levels and ACE activity were not found to be significantly affected by antihypertensive medication but were rather related to gender or genotype.

CONCLUSIONS

The data emphasize that antihypertensive treatment with different classes of drugs may modulate serum levels of neurohormones substantially resulting in distinct patterns of activation. These drug-related effects may require consideration when neurohormonal activation is of functional relevance or when neurohormones serve as prognostic predictors in patients with cardiovascular disorders.

Renin inhibition

Modification of the renin-angiotensin-aldosterone system by renin inhibitors may be an alternative to angiotensin-converting enzyme inhibitors in the treatment of cardiovascular disease. The development of clinically useful renin inhibitors has been hampered by a variety of pharmacologic problems, most notably the poor oral bioavailability of these peptide-related compounds. Peptidomimetic renin inhibitors that have been stabilized to enzymatic degradation in conjunction with optimizing physical characteristics amenable to intestinal absorption offer the greatest promise to date. Studies in animal models demonstrate that renin inhibitors are capable of reducing both systolic and diastolic blood pressures without causing reflex tachycardia. The response appears to be sustained with chronic administration. The beneficial cardiovascular effects of these compounds have been confirmed in the few studies conducted in patients with hypertension and in those with congestive heart failure. Further development of renin inhibitors is warranted.

Effects of nisoldipine on hypertension and glomerulosclerosis in Cohen diabetic rat with Goldblatt hypertension

Nisoldipine treatment for five months prevented a rise in blood pressure in Cohen diabetic rats with Goldblatt hypertension, compared to a significant elevation in untreated controls. Blood creatinine and urea also decreased significantly in the treated animals, and renal lesions were less severe. The prevalence of glomerulosclerosis, however, remained unaltered in both the treated and control groups. These findings indicate that increased blood pressure aggravates renal changes, while reducing it eliminates the aggravation.

Pharmacologic management of systemic hypertension in blacks

This article contrasts the characteristics of essential hypertension found in the black population with that seen in the nonblack population. Socioeconomic and pathophysiologic factors are discussed. Different pharmacologic classes of drugs are compared for their effectiveness in treating the black hypertensive patient. Because black hypertensives tend to have salt-sensitive, low-renin hypertension coupled with decreased cardiac output and high peripheral vascular resistance, an ideal antihypertensive should have natriuretic effects but also the physiologic capability of reducing vascular resistance. Such an ideal hypertensive drug would be able to lower systemic blood pressure while improving organ perfusion and function.

Calcium channel blockers in systemic hypertension

Alterations in transmembrane flux of calcium ions may be playing a role in the pathophysiology of systemic hypertension. Calcium channel blockers have been shown to be effective antihypertensive drugs with excellent safety profiles. They are efficacious in the long term treatment of systemic hypertension in all population subgroups, and have special applicability for treating patients with hypertensive urgencies and individuals with concomitant diseases such as angina pectoris and arrhythmias.

Angiotensin-converting enzyme inhibitors

In summary, ACE inhibitors are effective in reducing blood pressure as initial therapy in some hypertensive patients and in combination with diuretics and other agents in virtually all hypertensives. ACE inhibitors are uniquely advantageous because of their favorable hemodynamic effects, the lack of adverse metabolic effects, and their ability to prevent or blunt undesirable effects of diuretic therapy. Their safety in large numbers of hypertensives has been consistently demonstrated. The minor nature of most side effects and the rarity of life-threatening side effects of ACE inhibitors is reassuring. Clinical experience has provided information about patients likely to be at high risk for side effects with ACE inhibitors enabling avoidance of the drugs, or the use of small doses and careful scrutiny in such individuals. The development of this new class of drugs permits safe and effective blood pressure control with potential enhancement of the sense of well being and quality of life to a degree never before encountered.