Effects of losartan on catecholamine release in the isolated rat adrenal gland

Angiotensin II receptor blockers following intravenous nicardipine administration to lower blood pressure in patients with hypertensive intracerebral hemorrhage: a prospective randomized study

BACKGROUND AND OBJECTIVE

In patients with hypertensive intracerebral hemorrhage (HICH), intravenous nicardipine is primarily used to lower blood pressure (BP). However, there are few studies investigating the role of oral antihypertensives administered after intravenous nicardipine to prevent BP from rising. Angiotensin II receptor blockers (ARBs) may be beneficial in HICH patients not only as antihypertensives but also by lowering plasma catecholamine levels. A prospective randomized study was conducted between January 2015 and March 2016 to comparatively evaluate the efficacy of two ARBs (azilsartan vs. candesartan) following intravenous nicardipine administration on BP reduction.

PATIENTS AND METHODS

Thirty conscious HICH patients presenting within 6 h of symptom onset were enrolled (15 in each arm). After administering intravenous nicardipine for 24-48 h, the patients were randomized either to the azilsartan (20 mg) arm or to the candesartan (8 mg) arm. Frequency of hematoma expansion, 30-day modified Rankin scale, and temporal profiles of systolic blood pressure (SBP) and plasma norepinephrine/aldosterone were compared.

RESULTS

Substantial hematoma expansion occurred in two (13%) azilsartan patients and in one (7%) candesartan patient (P=1.00). SBPs were maintained at lower than 140±20 mmHg in both arms. Neither SBPs nor plasma norepinephrine/aldosterone levels differed significantly. All 30 patients had 30-day modified Rankin scale scores of 1-2.

CONCLUSION

Administration of ARBs following intravenous nicardipine effectively prevented BP from rising in HICH patients. However, whether BP should be strictly managed after 24 h of symptom onset should be addressed in future studies focusing not only on neurologic but also on cardiovascular and renal functions of HICH patients.

Influence of Fimasartan (a Novel AT(1) Receptor Blocker) on Catecholamine Release in the Adrenal Medulla of Spontaneously Hypertensive Rats

The aim of this study was to determine whether fimasartan, a newly developed AT₁ receptor blocker, can affect the CA release in the isolated perfused model of the adrenal medulla of spontaneously hypertensive rats (SHRs). Fimasartan (5~50 µM) perfused into an adrenal vein for 90 min produced dose- and time-dependently inhibited the CA secretory responses evoked by ACh (5.32 mM), high K⁺ (56 mM, a direct membrane depolarizer), DMPP (100 µM) and McN-A-343 (100 µM). Fimasartan failed to affect basal CA output. Furthermore, in adrenal glands loaded with fimasartan (15 µM), the CA secretory responses evoked by Bay-K-8644 (10 µM, an activator of L-type Ca²⁺ channels), cyclopiazonic acid (10 µM, an inhibitor of cytoplasmic Ca²⁺-ATPase), and veratridine (100 µM, an activator of Na⁺ channels) as well as by angiotensin II (Ang II, 100 nM), were markedly inhibited. In simultaneous presence of fimasartan (15 µM) and L-NAME (30 µM, an inhibitor of NO synthase), the CA secretory responses evoked by ACh, high K⁺, DMPP, Ang II, Bay-K-8644, and veratridine was not affected in comparison of data obtained from treatment with fimasartan (15 µM) alone. Also there was no difference in NO release between before and after treatment with fimasartan (15 µM). Collectively, these experimental results suggest that fimasartan inhibits the CA secretion evoked by Ang II, and cholinergic stimulation (both nicotininc and muscarinic receptors) as well as by membrane depolarization from the rat adrenal medulla. It seems that this inhibitory effect of fimasartan may be mediated by blocking the influx of both Na⁺ and Ca²⁺ through their ion channels into the rat adrenomedullary chromaffin cells as well as by inhibiting the Ca²⁺ release from the cytoplasmic calcium store, which is relevant to AT₁ receptor blockade without NO release.