Angiotensin-converting enzyme inhibition, the sympathetic nervous system, and congestive heart failure. The Australian Zestril (Lisinopril) Study Group

Beta2 adrenergic receptor gene Arg16Gly polymorphism is associated with therapeutic efficacy of benazepril on essential hypertension in Chinese

BACKGROUND

There is considerable variability in individual response to antihypertensive agents. The reason for this is not known, but may be related to individual genetic variability. This study examined whether the therapeutic efficacy of benazepril on essential hypertension is modified by beta2 adrenergic receptor gene (ADRB2) Arg16Gly (R16G) polymorphism.

METHODS AND RESULTS

We conducted a family-based study of 321 and 610 hypertensive subjects from Yuexi and Huoqiu Counties of Anhui, China, respectively. Both systolic and diastolic blood pressures (SBP and DBP) before and after a 15-day benazepril treatment were measured. ADRB2 R16G genotypes were determined for all subjects. ADRB2 G16 allele frequency was found to be 41.0% and. 47.4% in Huoqiu and Yuexi, respectively. In Yuexi family-based association test (FBAT) revealed that the G16 allele was associated with a greater DBP decrease in response to a 15-day benazepril treatment (Z = 2.12, P = 0.03), and the data were consistent with a dominant inheritance model. A similar trend was observed in Huoqiu Chinese, but the magnitudes of effects were smaller and did not reach statistical significance. The FBAT results were further confirmed by using a generalized estimating equation model.

CONCLUSION

Our family-based study provided the first evidence that ADRB2 R16G polymorphism may play an important role in DBP response to benazepril treatment, although the magnitude of the effect appears to be modified by other risk factors such as plasma lipid and glucose profiles.

Sympathetic tone assessed by washout of iodine 125-labeled metaiodobenzylguanidine from the murine left ventricle--influence of immobilization stress and inhibition of the renin-angiotensin system

BACKGROUND

Because it is not metabolized as is norepinephrine (NE), most of the metaiodobenzylguanidine (MIBG) taken up by the heart is considered to be lost subsequently by release concomitant with sympathetic stimulation. Therefore we examined whether the washout of MIBG is influenced by sympathetic tone, which we modulated by using immobilization stress or activation of the renin-angiotensin system (RAS).

METHODS AND RESULTS

In 175 male ddY mice, left ventricular radioactivity was counted 30 minutes or 4 hours after injection of 74 kBq (2 microCi) of iodine 125- or iodine 131-labeled MIBG (125I- or 131I-MIBG). The washout rates of MIBG were determined under immobilization stress or under sodium loading or restriction in combination with losartan (10 mg/kg) or cilazapril (1 mg/kg) pretreatment. Immobilization enhanced the washout of 125I-MIBG (80.9% vs 57.9% in the control animals); this was determined to be related to washout from the neuronal compartment, because the nonneuronal component assessed through desipramine pretreatment was not affected. Pretreatment with losartan or cilazapril decreased the facilitation of 125I-MIBG washout in sodium-restricted mice (40.9% and 33.7%, respectively, vs 43.5% in the control animals), but not in sodium-loaded mice.

CONCLUSIONS

Measurement of MIBG washout may be feasible for determining the changes in sympathetic tone caused by immobilization stress or activation of the RAS.

Angiotensin-converting enzyme inhibition and radial artery compliance in patients with congestive heart failure

Congestive heart failure is characterized by a clear-cut impairment of arterial compliance of medium-sized arteries, but whether this alteration is irreversible or can be favorably affected by cardiovascular drugs currently used in congestive heart failure treatment is unknown. We studied 9 congestive heart failure patients (New York Heart Association class II; age, [mean +/- SEM] 60.7 +/- 3.3 years) receiving diuretic and digitalis treatment in whom arterial compliance was assessed at the level of the radial artery by an echotracking device capable of measuring the arterial diameter along the entire cardiac cycle. Beat-to-beat arterial blood pressure was concomitantly measured by a Finapres device that allowed diameter-pressure curves and compliance-pressure curves (Langewouters' formula) to be calculated for the entire systolic-diastolic blood pressure range. Arterial compliance was expressed as the area under the compliance-pressure curve normalized for pulse pressure (compliance index). Data were collected before and after 4 and 8 weeks of oral administration of benazepril (10 mg/day). Ten healthy subjects were studied before and after an observational period of 4 weeks (5 subjects) or 8 weeks (5 subjects), and 9 age-matched mildly essential hypertensive subjects studied before and after 4 to 12 weeks of benazepril administration served as control subjects. In congestive heart failure patients, baseline compliance index was significantly less than in normotensive and hypertensive subjects. However, the compliance index showed a marked increase after 4 weeks of benazepril administration (+95.7 +/- 24.9%, P < .05); the increase was also marked after 8 weeks of angiotensin-converting enzyme inhibitor treatment (+77.7 +/- 4.2%, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)