Verapamil directly inhibits aldosterone synthesis by adrenal mitochondria in vitro

Risk of Developing Hypokalemia in Patients With Hypertension Treated With Combination Antihypertensive Therapy

Little is known about the occurrence of hypokalemia due to combination therapy for hypertension. Using data from Danish administrative registries, we investigated the association between different combinations of antihypertensive therapy and risk of developing hypokalemia. Using incidence density matching, 2 patients without hypokalemia were matched to a patient with hypokalemia (K, <3.5 mmol/L) on age, sex, renal function, and time between index date and date of potassium measurement. Combination therapies were subdivided into 10 groups including β-blockers (BB)+thiazides (BB+thiazides), calcium channel blockers (CCB)+renin angiotensin system inhibitors (RASi)+thiazides (CCB+RASi+Thiazides), calcium channel blockers+thiazides (CCB+thiazides), and β-blockers+renin angiotensin system inhibitors+thiazides (BB+RASi+thiazides). We used conditional logistic regression to estimate the odds of developing hypokalemia for different combinations of antihypertensive drugs within 90 days of combination therapy initiation. We matched 463 patients with hypokalemia to 926 patients with normal potassium concentrations. The multivariable analysis showed 5.82× increased odds of developing hypokalemia if administered CCB+thiazides (95% CI, 3.06–11.08) compared with CCB+RASi. Other combinations significantly associated with increased hypokalemia odds were BB+thiazides (odds ratio, 3.34 [95% CI, 1.67–6.66]), CCB+RASi+thiazides (odds ratio, 3.07 [95% CI, 1.72–5.46]), and BB+RASi+thiazides (odds ratio, 2.78 [95% CI, 1.41–5.47]). Combinations of thiazides with CCB, RASi, or BB were strongly associated with increased hypokalemia risk within 90 days of treatment initiation.

Differential effect of chronic inhibition of calcium channel and angiotensin II type 1-receptor on aldosterone synthesis in spontaneously hypertensive rats

We have investigated the in vivo effect of chronic blockade of Ca(2+)-channels and angiotensin II type 1 (AT(1))-receptors on aldosterone (Aldo)-synthesis in the adrenal glands of spontaneously hypertensive rats (SHR). Male SHR were administered Ca(2+)-antagonist, amlodipine (10 mg/kg per day) or AT(1)-receptor-antagonist, TCV-116 (1 mg/kg per day) from 7 until 11 weeks of age. Systolic blood pressure (SBP) and heart rate (HR) were significantly higher in SHR than Wistar-Kyoto (WKY) rats. Both treatments resulted in equivalent and significant reduction in SBP in SHR. Aldo-secretion in SHR, which was significantly higher than in WKY rats, was profoundly suppressed by TCV-116 compared with amlodipine. Both treatments resulted in thickening of the zona glomerulosa, which immunohistochemically contains Aldo, at the end of therapy. Competitive reverse transcription-polymerase chain reaction (RT-PCR) showed that CYP11A (P450scc) mRNA regulating the first step of Aldo-synthesis was significantly reduced from week 9 of age by amlodipine, and that CYP11B2 (P450aldo) mRNA regulating the last step of Aldo-synthesis was potently suppressed from 9 weeks of age by TCV-116. Our results indicate that chronic treatment with different antihypertensive agents directly modulates adrenocortical aldosterone synthesis in SHR in vivo via different mechanisms.

Effect of nilvadipine on adrenocortical cell proliferation and steroidogenesis in early stage of adrenal regeneration

The influence of nilvadipine, a novel calcium channel antagonist on adrenal regeneration was investigated in male Wistar rats. The estimation of the mitotic index after administration of colchicine was supplemented by an immunoperoxidase technique with monoclonal antibodies to bromodeoxyuridine. Plasma corticosterone was determined by a radioimmunological assay. Nilvadipine was given subcutaneously in two doses (0.2 and 1 mg/kg) to animals subjected to adrenal enucleation combined with contralateral adrenalectomy. It was found that nilvadipine inhibited the proliferation ratio of adrenocortical cells on the 4th day after surgery in a dose-dependent manner. The inhibitory effect of nilvadipine became less significant by 8 days after operation. However, no changes in corticosterone secretion were observed.