Abstract-Aldosterone is synthesized in extra-adrenal tissues, both blood vessels and brain. We undertook the present study to determine whether the rat heart produces aldosterone and to investigate the effects of adrenalectomy, ACE inhibition, and angiotensin II on aldosterone synthesis in the heart. To clarify the pathophysiological role of cardiac aldosterone in the hypertensive heart, we compared the synthesis of aldosterone in the hearts of stroke-prone spontaneously hypertensive rats (SHRSP) with that in Wistar-Kyoto rats. The effects of the aldosterone antagonist spironolactone on myocardial hypertrophy in adrenalectomized SHRSP were also studied. Isolated rat hearts were perfused for 2 hours, and the perfusate was analyzed with HPLC and mass spectrometry. The activity of aldosterone synthase was estimated on the basis of the conversion of [ 14 C]deoxycorticosterone to [ 14 C]aldosterone. The levels of aldosterone synthase gene (CYP11B2) mRNA were determined with competitive polymerase chain reaction. Aldosterone production, the activity of aldosterone synthase, and the expression of CYP11B2 mRNA were increased in hearts from adrenalectomized rats and rats treated with angiotensin II. ACE inhibitors decreased cardiac aldosterone synthesis. Cardiac aldosterone, aldosterone synthase activity, and CYP11B2 mRNA levels in hearts from 2-and 4-week-old SHRSP were significantly greater than those of age-matched Wistar-Kyoto rats. Spironolactone prevented cardiac hypertrophy in adrenalectomized SHRSP. These results suggest that the rat heart produces aldosterone and that endogenous cardiac aldosterone may affect cardiac function and hypertrophy in hypertension in rats. (Hypertension. 2000;36:495-500.)Key Words: heart Ⅲ rats, inbred strains Ⅲ aldosterone Ⅲ hypertrophy Ⅲ cytochrome p450 Ⅲ mRNA A ldosterone receptors are present in cardiac myocytes, endocardial endothelial cells, and cardiac fibroblasts. 1 The peripheral infusion of aldosterone in rats causes cardiac hypertrophy and cardiac fibrosis without increasing the blood pressure. 2 In cultured neonatal rat fibroblasts or cardiomyocytes, aldosterone increases collagen synthesis and protein synthesis. 3,4 Physiologically significant amounts of mineralocorticoids are believed to be synthesized only in the adrenal cortex. However, extra-adrenal steroid 21-hydroxylation and 11␤-hydroxylation occur in a variety of human tissues. Circulating progesterone is converted to deoxycorticosterone (DOC) and DOC sulfate in adult and fetal human extra-adrenal tissues. 5 The extra-adrenal expression of steroid 21-hydroxylase and 11␤-hydroxylase by a benign testicular Leydig cell tumor has also been reported. 6 We reported that aldosterone, synthesized in the vasculature, is in part controlled by angiotensin (Ang) II and participates in the development of vascular hypertrophy that correlates with Ang II concentration. 7,8 We performed the present study to determine whether the rat heart produces aldosterone and to investigate the effects of adrenalectomy, ACE inhibitor, and Ang ...

There have been several clinical studies examining the factors associated with cardiovascular disease (CVD) in patients with primary aldosteronism (PA); however, their results have left it unclear whether CVD is affected by the plasma aldosterone concentration or hypokalemia. We assessed the PA database established by the multicenter JPAS (Japan Primary Aldosteronism Study) and compared the prevalence of CVD among patients with PA with that among age-, sex-, and blood pressure-matched essential hypertension patients and participants with hypertension in a general population cohort. We also performed binary logistic regression analysis to determine which parameters significantly increased the odds ratio for CVD. Of the 2582 patients with PA studied, the prevalence of CVD, including stroke (cerebral infarction, cerebral hemorrhage, or subarachnoid hemorrhage), ischemic heart disease (myocardial infarction or angina pectoris), and heart failure, was 9.4% (stroke, 7.4%; ischemic heart disease, 2.1%; and heart failure, 0.6%). The prevalence of CVD, especially stroke, was higher among the patients with PA than those with essential hypertension/hypertension. Hypokalemia (K ≤3.5 mEq/L) and the unilateral subtype significantly increased adjusted odds ratios for CVD. Although aldosterone levels were not linearly related to the adjusted odds ratio for CVD, patients with plasma aldosterone concentrations ≥125 pg/mL had significantly higher adjusted odds ratios for CVD than those with plasma aldosterone concentrations <125 pg/mL. Thus, patients with PA seem to be at a higher risk of developing CVD than patients with essential hypertension. Moreover, patients with PA presenting with hypokalemia, the unilateral subtype, or plasma aldosterone concentration ≥125 pg/mL are at a greater risk of CVD and have a greater need for PA-specific treatments than others.

We have reported that aldosterone is synthesized and cytochrome P450aldo mRNA exists in the vasculature. To clarify the pathophysiological role of vascular aldosterone in hypertension, we compared aldosterone production in the mesenteric arteries of stroke-prone spontaneously hypertensive rats (SHRSP) with that in Wistar-Kyoto rats (WKY). The expressions of mRNA of cytochrome P450aldo, mineralocorticoid receptor, and alpha 1, Na,K-ATPase in the mesenteric arteries were compared between the two groups. Aldosterone concentration in the perfusate of the vasculature was measured by radioimmunoassay after purification with high-performance liquid chromatography. Cytochrome P450aldo and mineralocorticoid receptor mRNA levels were quantified by Southern blot analysis of the products of reverse-transcribed polymerase chain reaction. Levels of alpha 1 Na,K-ATPase mRNA were measured by Northern blot analysis. Vascular aldosterone and cytochrome P450aldo mRNA levels of 2-week-old SHRSP were significantly increased compared with those of age-matched WKY. However, vascular aldosterone in 4- and 9-week-old SHRSP did not differ from that in age-matched WKY. Expression levels of mineralocorticoid receptor mRNA in the vasculature of 4- and 9-week-old SHRSP were significantly increased compared with those in age-matched WKY. Concentrations of vascular alpha 1 Na,K-ATPase mRNA of 2-, 4-, and 9-week-old SHRSP also were significantly higher than those in age-matched WKY. These results suggest that vascular aldosterone contributes to the pathophysiology of hypertension in SHRSP in the early stage.

Angiotensin I (Ang I), Ang II, angiotensinogen, and renin are formed locally in the vasculature. We undertook this study to determine whether the rat mesenteric artery produces aldosterone and to investigate the effects of adrenalectomy, an angiotensin-converting enzyme inhibitor, Ang II, or potassium on aldosterone production in vascular tissue. Isolated rat mesenteric arteries were perfused with Krebs-Ringer solution for 4 hours. The perfusate was collected and chromatographed in a reversed-phase high-performance liquid chromatographic (HPLC) system. The fraction corresponding to synthetic aldosterone was collected and analyzed by mass spectrometry. The aldosterone concentration in the perfusate from the adrenalectomized rats and rats treated with an angiotensin-converting enzyme inhibitor was measured using radioimmunoassay after HPLC separation. The mass spectra of synthetic aldosterone and aldosterone isolated from the perfusate of rat mesenteric arteries were identical. Aldosterone production in the mesenteric arteries of adrenalectomized rats was increased and of rats treated with an angiotensin-converting enzyme inhibitor was reduced compared with that of controls. Ang II (1.9 x 10(10) mol/L) and potassium (6.0 mmol/L) increased aldosterone production in mesenteric arteries. This study shows that the rat mesenteric artery produces aldosterone and that the intravascular renin-angiotensin-aldosterone system may contribute to vascular tone.

To investigate the prevalence and causes of diabetes in patients with primary aldosteronism (PA) in a multi-institutional cohort study in Japan. RESEARCH DESIGN AND METHODS The prevalence of diabetes was determined in 2,210 patients with PA (diagnosed or glycated hemoglobin [HbA 1c ] ‡6.5% [ ‡48 mmol/mol]; NGSP) and compared with that of the Japanese general population according to age and sex. In 1,386 patients with PA and clear laterality (unilateral or bilateral), the effects of plasma aldosterone concentration (PAC), hypokalemia (<3.5 mEq/L), suspected subclinical hypercortisolism (SH; serum cortisol ‡1.8 mg/dL after 1-mg dexamethasone suppression test), and PA laterality on the prevalence of diabetes or prediabetes (5.7% £ HbA 1c <6.5% [39 mmol/mol £ HbA 1c <48 mmol/mol]) were examined. RESULTS Of the 2,210 patients with PA, 477 (21.6%) had diabetes. This prevalence is higher than that in the general population (12.1%) or in 10-year cohorts aged 30-69 years. Logistic regression or x 2 test revealed a significant contribution of suspected SH to diabetes. Despite more active PA profiles (e.g., higher PAC and lower potassium concentrations) in unilateral than bilateral PA, BMI and HbA 1c values were significantly higher in bilateral PA. PA laterality had no effect on the prevalence of diabetes; however, the prevalence of prediabetes was significantly higher in bilateral than unilateral PA. CONCLUSIONS Individuals with PA have a high prevalence of diabetes, which is associated mainly with SH. The prevalence of prediabetes is greater for bilateral than unilateral PA, suggesting a unique metabolic cause of bilateral PA.

Mineralocorticoids have been suggested to act on blood vessels, leading to increased vasoreactivity and peripheral resistance. Aldosterone is synthesized locally in blood vessels and participates in the hypertrophy of vascular smooth muscle cells. In this study we examined the effects of angiotensin II (ANG II), potassium, and ACTH on the production of aldosterone, the activity of aldosterone synthase, and the expression of CYP11B2 and CYP11B1 messenger ribonucleic acid (mRNA) in cultured human vascular endothelial cells. Human vascular endothelial cells were incubated with ANG II, potassium, or ACTH with or without [14C]deoxycorticosterone ([14C]DOC). Incubation medium was collected, and chromatography was preformed in a reverse phase high performance liquid chromatography system. The concentration of aldosterone in the incubation medium was measured using RIA after separation with the high performance liquid chromatography system. The activity of aldosterone synthase was estimated by the conversion of [14C]DOC to [14C]aldosterone. The levels of CYP11B2 and CYP11B1 mRNA were determined by competitive PCR. ANG II, potassium, and ACTH increased the production levels of aldosterone in a dose-dependent fashion. Both ANG II and potassium increased the conversion of [14C]DOC to [14C]aldosterone, but ACTH did not significantly increase the conversion. Both ANG II and potassium increased the concentration of CYP11B2 mRNA, but not that of CYP11B1 mRNA. Tumor necrosis factor reduced ANG II- and potassium-induced aldosterone synthesis and CYP11B2 mRNA levels. ACTH did not influence the expression of CYP11B2 mRNA. These results suggest that vascular aldosterone synthase is controlled by ANG II and potassium at the transcriptional level.

In DS rats, blockade of aldosterone or Ang II protects cardiac hypertrophy and fibrosis by inactivation of the local RAAS in the heart.

Recent studies have reported a high prevalence of primary aldosteronism among patients with severe hypertension. However, the prevalence of this disease among normotensive and mildly hypertensive patients has not been determined. The aim of this study was to examine the prevalence of primary aldosteronism among prehypertensive and stage 1 hypertensive subjects. A total of 292 adult subjects with hypertension or prehypertension was screened for primary aldosteronism. Subjects with a plasma aldosterone concentration (ng per 100 ml) to plasma renin activity (ng ml -1 h -1 ) ratio (ARR) above 20 underwent confirmatory captopril suppression testing. A total of 54 subjects (18.5%) had an ARR above 20. A captopril suppression test was performed in 17 of 54 subjects with probable primary aldosteronism. The test confirmed the diagnosis of primary aldosteronism in 11 (64.7%) of 17 patients, giving a least prevalence of 3.8% for this disease. The 11 patients with primary aldosteronism had a mean ± s.d. systolic blood pressure of 139 ± 4 mm Hg, diastolic blood pressure of 95 ± 10 mm Hg and serum potassium of 4.46 ± 0.48 mEq l -1 at the time of screening test. The prevalence of primary aldosteronism as could be assessed in this study was at least 6.8% in prehypertensive patients, 3.3% in stage 1 hypertensive patients and 3.1% in stage 2 hypertensive patients. In conclusion, this study suggests a high prevalence of primary aldosteronism among prehypertensive and stage 1 hypertensive Japanese patients. Significant numbers of prehypertensive individuals may have subclinical forms of this disease.