• The Korean Journal of Physiology and Pharmacology
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• v.17 no.1
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• pp.99-109
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• 2013

The aim of this study was to determine whether fimasartan, a newly developed $AT_1$ receptor blocker, can affect the CA release in the isolated perfused model of the adrenal medulla of spontaneously hypertensive rats (SHRs). Fimasartan (5~50 ${\mu}M$) 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 ${\mu}M$) and McN-A-343 (100 ${\mu}M$). Fimasartan failed to affect basal CA output. Furthermore, in adrenal glands loaded with fimasartan (15 ${\mu}M$), the CA secretory responses evoked by Bay-K-8644 (10 ${\mu}M$, an activator of L-type $Ca^{2+}$ channels), cyclopiazonic acid (10 ${\mu}M$, an inhibitor of cytoplasmic $Ca^{2+}$-ATPase), and veratridine (100 ${\mu}M$, an activator of $Na^+$ channels) as well as by angiotensin II (Ang II, 100 nM), were markedly inhibited. In simultaneous presence of fimasartan (15 ${\mu}M$) and L-NAME (30 ${\mu}M$, 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 ${\mu}M$) alone. Also there was no difference in NO release between before and after treatment with fimasartan (15 ${\mu}M$). 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 $Ca^{2+}$ through their ion channels into the rat adrenomedullary chromaffin cells as well as by inhibiting the $Ca^{2+}$ release from the cytoplasmic calcium store, which is relevant to $AT_1$ receptor blockade without NO release.

• The Korean Journal of Physiology and Pharmacology
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• v.11 no.3
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• pp.97-106
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• 2007

The present study was attempted to investigate the effect of nicorandil, which is an ATP-sensitive potassium ($K_{ATP}$) channel opener, on secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane depolarization from the isolated perfused rat adrenal glands. The perfusion of nicorandil ($0.3{\sim}3.0mM$) into an adrenal vein for 90 min produced relatively dose-and time-dependent inhibition in CA secretion evoked by ACh (5.32 mM), high $k^+$ (a direct membrane depolarizer, 56 mM), DMPP (a selective neuronal nicotinic receptor agonist, $100{\mu}M$ for 2 min), McN-A-343 (a selective muscarinic $M_1$ receptor agonist, $100{\mu}M$ for 4 min), Bay-K-8644 (an activator of L-type dihydropyridine $Ca^{2+}$ channels, $10{\mu}M$ for 4 min) and cyclopiazonic acid (an activator of cytoplasmic $Ca^{2+}$-ATPase, $10{\mu}M$ for 4 min). In adrenal glands simultaneously preloaded with nicorandil (1.0 mM) and glibenclamide (a nonspecific $K_{ATP}$-channel blocker, 1.0 mM), the CA secretory responses evoked by ACh, high potassium, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were recovered to the considerable extent of the control release in comparison with that of nicorandil-treatment only. Taken together, the present study demonstrates that nicorandil inhibits the adrenal CA secretion in response to stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as by membrane depolarization from the isolated perfused rat adrenal glands. It seems that this inhibitory effect of nicorandil may be mediated by inhibiting both $Ca^{2+}$ influx and the $Ca^{2+}$ release from intracellular store through activation of $K_{ATP}$ channels in the rat adrenomedullary chromaffin cells. These results suggest that nicorandil-sensitive $K_{ATP}$ channels may play an inhibitory role in the regulation of the rat adrenomedullary CA secretion.

• The Korean Journal of Physiology and Pharmacology
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• v.18 no.5
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• pp.431-439
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• 2014

The aim of the present study was to investigate whether ginsenoside-Rb2 (Rb2) can affect the secretion of catecholamines (CA) in the perfused model of the rat adrenal medulla. Rb2 ($3{\sim}30{\mu}M$), perfused into an adrenal vein for 90 min, inhibited ACh (5.32 mM)-evoked CA secretory response in a dose- and time-dependent fashion. Rb2 ($10{\mu}M$) also time-dependently inhibited the CA secretion evoked by DMPP ($100{\mu}M$, a selective neuronal nicotinic receptor agonist) and high $K^+$ (56 mM, a direct membrane depolarizer). Rb2 itself did not affect basal CA secretion (data not shown). Also, in the presence of Rb2 ($50{\mu}g/mL$), the secretory responses of CA evoked by veratridine (a selective $Na^+$ channel activator ($50{\mu}M$), Bay-K-8644 (an L-type dihydropyridine $Ca^{2+}$ channel activator, $10{\mu}M$), and cyclopiazonic acid (a cytoplasmic $Ca^{2+}$-ATPase inhibitor, $10{\mu}M$) were significantly reduced, respectively. Interestingly, in the simultaneous presence of Rb2 ($10{\mu}M$) and L-NAME (an inhibitor of NO synthase, $30{\mu}M$), the inhibitory responses of Rb2 on ACh-evoked CA secretory response was considerably recovered to the extent of the corresponding control secretion compared with the inhibitory effect of Rb2-treatment alone. Practically, the level of NO released from adrenal medulla after the treatment of Rb2 ($10{\mu}M$) was greatly elevated compared to the corresponding basal released level. Collectively, these results demonstrate that Rb2 inhibits the CA secretory responses evoked by nicotinic stimulation as well as by direct membrane-depolarization from the isolated perfused rat adrenal medulla. It seems that this inhibitory effect of Rb2 is mediated by inhibiting both the influx of $Ca^{2+}$ and $Na^+$ into the adrenomedullary chromaffin cells and also by suppressing the release of $Ca^{2+}$ from the cytoplasmic calcium store, at least partly through the increased NO production due to the activation of nitric oxide synthase, which is relevant to neuronal nicotinic receptor blockade.

• Biomolecules & Therapeutics
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• v.10 no.3
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• pp.142-151
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• 2002

The present study was attempted to investigate the effect of apamin on catecholamine (CA) secretion evoked by ACh, high $K^+$, DMPP, McN-A-343, cyclopiazonic acid and Bay-K-8644 from the isolated perfused rat adrenal gland and to establish the mechanism of its action. The perfusion of apamin (1 nM) into an adrenal vein for 20 min produced greatly potentiation in CA secretion evoked by ACh (5.32 $ imes$ $10^{-3}$ M), high $K^+$, (5.6 $ imes$ $10^{-2}$), DMPP ($10^{-4}$ M for 2 min), McN-A-343 ($10^{-4}$ M for 2 min), cyclopiazonic acid ($10^{-5}$ M for 4 min) and Bay-K-8644 ($10^{-5}$ M for 4 min). However, apamin itself did fail to affect basal catecholamine output. Furthermore, in adrenal glands preloaded with apamin (1 nM) under the presence of glibenclamide ($10^{-6}$ M), an antidiabetic sulfonylurea that has been shown to be a specific blocker of ATP-regulated potassium channels (for 20 min), CA secretion evoked by DMPP and McN-A-343 was not affected. However, the perfusion of high concentration of apamin (100 nM) into an adrenal vein for 20 min rather inhibited significantly CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, cyclopiazonic acid and Bay-K-8644. Taken together, these results suggest that the low concentration of apamin causes greatly the enhancement of CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as by membrane depolarization. These findings suggests that apamin-sensitive SK ($Ca^{2+}$) channels located in rat adrenal medullary chromaffin cells may play an inhibitory role in the release of catecholamines mediated by stimulation of cholinergic nicotinic and muscarinic receptors as well as membrane depolarization. However, it is thought that high concentration of apamin cause the inhibitory responses in catecholamine secretion evoked by stimulation of cholinergic receptors as well as by membrane depolarization from the rat adrenal gland without relevance with the SK channel blockade.

• Natural Product Sciences
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• v.13 no.1
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• pp.68-77
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• 2007

The aim of the present study was to examine the effects of green tea extract (CUMS6335) on the release of CA evoked by cholinergic stimulation and direct membrane-depolarization in the perfused model of the adrenal gland isolated from the spontaneously hypertensive rats (SHRs), and to establish the mechanism of action. Furthermore, it was also to test whether there is species difference between animals, and between CUMS6335 and EGCG, one of biologically the most powerful catechin compounds found in green tea. CUMS6335 $(100\;{\mu}g/ml)$, when perfused into an adrenal vein for 60 min, time-dependently inhibited the CA secretory responses evoked by ACh (5.32mM), high $K^+$(56 mM), DMPP $(100\;{\mu}M)$, and McN-A-343 $(100\;{\mu}M)$ from the isolated perfused adrenal glands of SHRs. However, CUMS6335 itself did fail to affect basal catecholamine output. Also, in adrenal glands loaded with CUMS6335 $(100\;{\mu}g/ml)$, the CA secretory responses evoked by Bay-K-8644 $(10\;{\mu}M)$ and cyclopiazonic acid $(10\;{\mu}M)$ were also inhibited in a relatively time-dependent fashion. However, in the Presence of EGCG $(8.0\;{\mu}g/ml)$ for 60 min, the CA secretory response evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were not affected except for last period. Collectively, these results indicate that CUMS6335 inhibits the CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as by direct membrane-depolarization from the perfused adrenal gland of the SHR. It seems that this inhibitory effect of CUMS6335 is exerted by blocking both the calcium influx into the rat adrenal medullary chromaffin cells and the uptake of $Ca^{2+}$ into the cytoplasmic calcium store, which are at least partly relevant to the direct interaction with the nicotinic receptor itself. It seems likely that there is much difference in mode of the CA-releasing action between CUMS6335 and EGCG.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.1
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• pp.13-23
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• 2008

The aim of the present study was designed to establish comparatively the inhibitory effects of $D_1$-like and $D_2$-like dopaminergic receptor agonists, SKF81297 and R(-)-TNPA on the release of catecholamines (CA) evoked by cholinergic stimulation and membrane depolarization from the isolated perfused model of the rat adrenal medulla. SKF81297 $(30{\mu}M)$ and R-(-)-TNPA $(30{\mu}M)$ perfused into an adrenal vein for 60 min, produced great inhibition in the CA secretory responses evoked by ACh $(5.32{\times}10^{-3}\;M)$, DMPP $(10^{-4}\;M)$, McN-A-343 $(10^{-4}\;M)$, high $K^+$ $(5.6{\times}10^{-2}\;M)$, Bay-K-8644 $(10{\mu}M)$, and cyclopiazonic acid $(10{\mu}M)$, respectively. For the release of CA evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid, the following rank order of inhibitory potency was obtained: SKF81297>R-(-)-TNPA. However, R(+)-SCH23390, a selectve $D_1$-like dopaminergic receptor antagonist, and S(-)-raclopride, a selectve $D_2$-like dopaminergic receptor antagonist, enhanced the CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid only for $0{\sim}4$ min. The rank order for the enhancement of CA release evoked by high $K^+$, McN-A-343 and cyclopiazonic acid was R(+)-SCH23390>S(-)-raclopride. Also, the rank order for ACh, DMPP and Bay-K-8644 was S(-)-raclopride > R(+)-SCH23390. Taken together, these results demonstrate that both SKF81297 and R-(-)-TNPA inhibit the CA release evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors and the membrane depolarization from the isolated perfused rat adrenal gland without affecting the basal release, respectively, but both R(+)-SCH23390 and S(-)-raclopride facilitate the CA release evoked by them. It seems likely that the inhibitory effects of SKF81297 and R-(-)-TNPA are mediated by the activation of $D_1$-like and $D_2$-like dopaminergic receptors located on the rat adrenomedullary chromaffin cells, respectively, whereas the facilitatory effects of R(+)-SCH23390 and S(-)-raclopride are mediated by the blockade of $D_1$-like and $D_2$-like dopaminergic receptors, respectively: this action is possibly associated with extra- and intracellular calcium mobilization. Based on these results, it is thought that the presence of dopaminergic $D_1$ receptors may play an important role in regulation of the rat adrenomedullary CA secretion, in addition to well-known dopaminergic $D_2$ receptors.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.4
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• pp.223-230
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• 2005

The purpose of the present study was to examine the effect of naltrexone, an opioid antagonist, on secretion of catecholamines (CA) evoked by cholinergic nicotinic stimulation and membrane-depolarization from the isolated perfused rat adrenal gland and to establish the mechanism of its action. Naltrexone $(3{\times}10^{-6}M)$ perfused into an adrenal vein for 60 min produced time-dependent inhibition in CA secretory responses evoked by ACh $(5.32{\times}10^{-3}M)$ , high $K^+$ $(5.6{\times}10^{-2}M)$ , DMPP ($10^{-4}$ M) and McN-A-343 $(10^{-4}M)$ . Naltrexone itself did also fail to affect basal CA output. In adrenal glands loaded with naltrexone $(3{\times}10^{-6}M)$ , the CA secretory responses evoked by Bay-K-8644, an activator of L-type $Ca^{2+}$ channels and cyclopiazonic acid, an inhibitor of cytoplasmic $Ca^{2+}-ATPase$, were also inhibited. However, in the presence of met-enkephalin $(5{\times}10^{-6}M)$ , a well-known opioid agonist, the CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly inhibited. Collectively, these experimental results demonstrate that naltrexone inhibits greatly CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as that by membrane depolarization. It seems that this inhibitory effect of naltrexone does not involve opioid receptors, but might be mediated by blocking both the calcium influx into the rat adrenal medullary chromaffin cells and the uptake of $Ca^{2+}$ into the cytoplasmic calcium store, which are at least partly relevant to the direct interaction with the nicotinic receptor itself.

• Development and Reproduction
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• v.2 no.1
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• pp.39-43
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• 1998

The synthesis of steroid hormone starts from cholesterol. Steroidogenic acute regulatory protein(StAR) transfers cholesterol acutely from the outer mitochondrial membranes to the inner in the early step of steroidogenesis. Many kinds of steroid hormones are mainly synthesized in adrenal grand, ovary and testis. The purpose of this study is to determine the distribution of StAR mRNA in the rat ovary and adrenal gland and to confirm the functions of StAR in these organs. In the ovary, StAR mRNAs were strongly expressed in the corpus luteum, where progesterone is synthesized, and these were weakly expressed in the theca layer of follicles, where androgen is synthesized. However, StAR mRNAs were not detected in the estrogen producing granulosa cells of growing follicles. In the corpus luteum, StAR mRNAs were strongly loclized in the zona fasciculata and zona reticularis, where glucocorticoid is mainly synthesized. StAR mRNAs were weakly expressed in the zona gromerulosa, where mineralcorticoid is synthesized. StAR mRNAs were not detected in the adrenal medulla. In our results, StAR mRNAs were expressed differentially in the steroidogenic cells of ovary and adrenal gland according to the types of steroid hormones, and the statges of corpus luteum development. We conclude that StAR is involved in the steroidogenesis at the very early step of steroid synthesis cascade.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.173-184
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• 1998

The present study was undertaken to examine the influence of glucocorticoids on the secretory responses of catecholamines (CA) evoked by acetylcholine (ACh), DMPP, McN-A-343, excess K^+$ and Bay-K-8644 from the isolated perfused rat adrenal gland and to clarify the mechanism of its action. The perfusion of the synthetic glucocorticoid dexamethasone (10-100\;{\mu}M$) into an adrenal vein for 20 min produced a dose-dependent inhibition in CA secretion evoked by ACh (5.32 mM), excess K^+$ (a membrane-depolarizor 56 mM), DMPP (a selective nicotinic receptor agonist, 100\;{\mu}M$ for 2 min), McN-A-343 (a muscarinic receptor agonist, 100\;{\mu}M$ for 4 min), Bay-K-8644 (a calcium channel activator, 10\;{\mu}M$ for 4 min) and cyclopiazonic acid (a releaser of intracellular $Ca^{2+}$, 10\;{\mu}M$ for 4 min). Similarly, the preperfusion of hydrocortisone (30\;{\mu}M$) for 20 min also attenuated significantly the secretory responses of CA evoked by nicotinic and muscarinic receptor stimulation as well as membrane-depolarization, $Ca^{2+}$ channel activation and the release of intracellular $Ca^{2+}$. Furthermore, even in the presence of betamethasone (30{\mu}M$), CA secretion evoked by ACh, excess K^+$, DMPP and McN-A-343 was also markedly inhibited. Taken together, the present results suggest that glucocorticoids cause the marked inhibition of CA secretion evoked by both cholinergic nicotinic and muscarinic receptor stimulation from the isolated perfused rat adrenal gland, indicating strongly that this inhibitory effect may be mediated by inhibiting influx of extracellular calcium as well as the release of intracellular calcium in the rat adrenomedullary chromaffin cells.

• Nutrition Research and Practice
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• v.4 no.4
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• pp.270-275
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• 2010

Catecholamines are among the first molecules that displayed a kind of response to prolonged or repeated stress. It is well established that long-term stress leads to the induction of catecholamine biosynthetic enzymes such as tyrosine hydroxylase (TH) and dopamine ${\beta}$-hydroxylase (DBH) in adrenal medulla. The aim of the present study was to evaluate the effects of ginseng on TH and DBH mRNA expression. Repeated (2 h daily, 14 days) immobilization stress resulted in a significant increase of TH and DBH mRNA levels in rat adrenal medulla. However, ginseng treatment reversed the stress-induced increase of TH and DBH mRNA expression in the immobilization-stressed rats. Nicotine as a ligand of the nicotinic acetylcholine receptor (nAChR) in adrenal medulla stimulates catecholamine secretion and activates TH and DBH gene expression. Nicotine treatment increased mRNA levels of TH and DBH by 3.3- and 3.1-fold in PC12 cells. The ginseng total saponin exhibited a significant reversal in the nicotine-induced increase of TH and DBH mRNA expression, decreasing the mRNA levels of TH and DBH by 57.2% and 48.9%, respectively in PC12 cells. In conclusion, immobilization stress induced catecholamine biosynthetic enzymes gene expression, while ginseng appeared to restore homeostasis via suppression of TH and DBH gene expression. In part, the regulatory activity in the TH and DBH gene expression of ginseng may account for the anti-stress action produced by ginseng.