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 (3~30 microM), 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 microM) also time-dependently inhibited the CA secretion evoked by DMPP (100 microM, 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 microg/mL), the secretory responses of CA evoked by veratridine (a selective Na+ channel activator (50 microM), Bay-K-8644 (an L-type dihydropyridine Ca2+ channel activator, 10 microM), and cyclopiazonic acid (a cytoplasmic Ca2+-ATPase inhibitor, 10 microM) were significantly reduced, respectively. Interestingly, in the simultaneous presence of Rb2 (10 microM) and L-NAME (an inhibitor of NO synthase, 30 microM), 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 microM) 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 Ca2+ and Na+ into the adrenomedullary chromaffin cells and also by suppressing the release of Ca2+ 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.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Medulla ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Membranes ; Neurons ; NG-Nitroarginine Methyl Ester ; Nitric Oxide Synthase ; Rats ; Receptors, Nicotinic ; Veins ; Veratridine

Effect of acetylcholine(ACh) and McN-A-343 on porcine coronary artery and rabbit thoracic aorta were investigated in isolated preparations with or without intact endothelium. In the porcine coronary artery, ACh produced concentration dependent contraction which was greater in rings without the endothelium than in intact endothelial rings, but McN-A-343 did not alter the basel tension in both tissues. ACh relaxed contraction induced by 5-hydroxytryptamine(5-HT) in only intact endothelial rings, while NcN-A-343 inhibited the 5-HT induced tension in both preparations dose dependently. Carbachol elicited a prominent contraction in both tissues. The carbacol-induced tension was markedly inhibited by McN-A-343 in either rings with or without endothelium, while ACh contracted further the tension. ACh and McN-A-343 did not after the KCi induced tension, but clearly potentiated the contraction induced by Bay K 8644 in intact endothelial rings. In rabbit thoracic aorta, ACh elicited contraction in a concentration-dependent fashion which was potentiated by removal of endothelium, but McN-A-343 did not affect the basal tension of both rings. ACh inhibited the 5-HT-induced contraction in only intact endothelial ring, but McN-A-343 did not change the contraction of both rings. Conclusively, ACh produces endothelium-dependent relaxation in both arteries, while McN-A-343 elevated endothelium-independent inhibition to 5-HT or carbachol-induced tension.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride* ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Acetylcholine* ; Aorta, Thoracic ; Arteries* ; Carbachol ; Coronary Vessels ; Endothelium ; Relaxation ; Serotonin

The aim of the present study was designed to establish comparatively the inhibitory effects of D1-like and D2-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 micrometer) and R-(-)-TNPA (30 micrometer) perfused into an adrenal vein for 60 min, produced great inhibition in the CA secretory responses evoked by ACh (5.32x10(-3) M), DMPP (10(-4) M), McN-A-343 (10(-4) M), high K+ (5.6x10(-2) M), Bay-K-8644 (10 micrometer), and cyclopiazonic acid (10 micrometer), 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 D1-like dopaminergic receptor antagonist, and S(-)-raclopride, a selectve D2-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 0~4 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 D1-like and D2-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 D1-like and D2-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 D1 receptors may play an important role in regulation of the rat adrenomedullary CA secretion, in addition to well-known dopaminergic D2 receptors.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands ; Adrenal Medulla ; Animals ; Benzazepines ; Calcium ; Catecholamines ; Chromaffin Cells ; Dimethylphenylpiperazinium Iodide ; Indoles ; Membranes ; Rats ; Veins

The aim of the present study was to investigate the effects of 6-chloro-7,8-dihydroxy-1-phenyl-2,3, 4,5-tetrahydro-1H-3-benzazepine (SKF81297), a selective agonist of dopaminergic D1 receptor, on the secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane-depolarization in the isolated perfused rat adrenal gland, and also to elucidate the mechanism involved. SKF81297 (10~100microM) perfused into an adrenal vein for 60 min produced dose- and time-dependent inhibition of CA secretory responses evoked by ACh (5.32 mM), high K+ (56 mM), DMPP (100microM) and McN-A-343 (100microM). Also, in adrenal glands loaded with SKF81297 (30microM), the CA secretory responses evoked by Bay-K-8644 (10microM), an activator of L-type Ca2+ channels and cyclopiazonic acid (10microM), an inhibitor of cytoplasmic Ca2+-ATPase were also inhibited. However, in the presence of the dopamine D1 receptor antagonist, (R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-benzazepine-7-ol (SCH23390, 3microM), which is a selective antagonist of dopaminergic D1 receptor, the inhibitory responses of SKF81297 (30microM) on the CA secretion evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644, and cyclopiazonic acid were significantly reduced. Collectively, these experimental results suggest that SKF81297 inhibits the CA secretion from the rat adrenal medulla evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) and membrane depolarization. This inhibitory of SKF81297 seems to be mediated by stimulation of dopaminergic D1 receptors located on the rat adrenomedullary chromaffin cells, which are relevant to extra- and intracellular calcium mobilization. Therefore, it is thought that the presence of the dopaminergic D1 receptors may be involved in regulation of CA release in the rat adrenal medulla.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands ; Adrenal Medulla* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Membranes ; Rats* ; Receptors, Dopamine D1 ; Veins

The present study was undertaken to investigate the effect of doxorubicin (DX) on secretion of catecholamines (CA) evoked by ACh, high K+, DMPP and McN-A-343 from the isolated perfused rat adrenal gland and to establish the mechanism of its action. DX (10(-7)~10(-6) M) perfused into an adrenal vein for 60 min produced relatively dose- and time-dependent inhibition of CA secretory responses evoked by ACh (5.32 X 10(-3) M), DMPP (10(-4) M) and McN-A-343 (10(-4) M). However, lower dose of DX did not affect CA secretion by high K+ (5.6 X 10(-2) M), but its higher doses depressed time-dependently CA secretion evoked by high K+. DX itself did also fail to affect basal CA output. In adrenal glands loaded with DX (3 X 10(-7) M), CA secretory responses evoked by Bay-K-8644, an activator of L-type Ca2+ channels and cyclopiazonic acid, an inhibitor of cytoplasmic Ca2+-ATPase were time-dependently inhibited. Furthermore, daunorubicin (3 X 10(-7) M), given into the adrenal gland for 60 min, attenuated CA secretory responses evoked by ACh, high K+, DMPP and McN-A-343. Taken together, these results suggest that DX causes relatively dose- and time-dependent inhibition of CA secretory responses evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors from the isolated perfused rat adrenal gland. However, lower dose of DX did not affect CA secretion by high K+, and higher doses of DX reduced time-dependently CA secretion of high K+. It is thought that these effects of DX may be mediated by inhibiting both influx of extracellular calcium into the rat adrenomedullary chromaffin cells and intracelluar calcium release from the cytoplasmic store. Also, there was no difference in the mode of action between DX and daunorubicin in rat adrenomedullary CA secretion.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Daunorubicin ; Dimethylphenylpiperazinium Iodide ; Doxorubicin* ; Rats* ; Veins

The present study was designed to clarify whether tacrine affects the release of catecholamines (CA) from the isolated perfused model of rat adrenal gland or not and to elucidate the mechanism of its action. Tacrine (3 X 10(-5)~3 X 10(-4) M) perfused into an adrenal vein for 60 min inhibited CA secretory responses evoked by ACh (5.32 X 10(-3) M), DMPP (a selective neuronal nicotinic agonist, 10(-4) M for 2 min) and McN-A-343 (a selective muscarinic M1-agonist, 10(-4) M for 2 min) in relatively dose- and time- dependent manners. However, tacrine failed to affect CA secretion by high K+ (5.6 X 10(-2) M). Tacrine itself at concentrations used in the present experiments did not also affect spontaneous CA output. Furthermore, in the presence of tacrine (10(-4) M), CA secretory responses evoked by Bay-K-8644 (an activator of L-type Ca2+ channels, 10(-4) M), but not by cyclopiazonic acid (an inhibitor of cytoplasmic Ca2+-ATPase, 10(-4) M), was relatively time-dependently attenuated. Also, physostigmine (10(-4) M), given into the adrenal gland for 60 min, depressed CA secretory responses evoked by ACh, McN-A-343 and DMPP while did not affect that evoked by high K+. Collectively, these results obtained from the present study demonstrate that tacrine greatly inhibits CA secretion from the perfused rat adrenal gland evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors, but does fail to affect that by direct membrane-depolarization. It is suggested that this inhibitory effect of tacrine may be exerted by blocking both the calcium influx into the rat adrenal medullary chromaffin cells without Ca2+ release from the cytoplasmic calcium store, that is relevant to the cholinergic blockade. Also, the mode of action between tacrine and physostigmine in rat adrenomedullary CA secretion seems to be similar.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Neurons ; Nicotinic Agonists ; Physostigmine ; Rats* ; Tacrine* ; Veins

The aim of the present study was to investigate the effects of R-(-)-2,10,11-trihydroxy-N-propylnoraporphine [R-(-)-TNPA], a selective agonist of dopaminergic D2 receptor and S(-)-raclopride, a selective antagonist of dopaminergic D2 receptor, on the secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane-depolarization in the isolated perfused model of the rat adrenal gland, and also to establish its mechanism of action. R-(-)-TNPA (10~100 micrometer) perfused into an adrenal vein for 60 min produced dose- and time-dependent inhibition in CA secretory responses evoked by ACh (5.32 mM), high K+ (56 mM), DMPP (100 micrometer) and McN-A-343 (100 micrometer). R-(-)-TNPA itself did also fail to affect basal CA output. Also, in adrenal glands loaded with R-(-)-TNPA (30 micrometer), the CA secretory responses evoked by Bay-K-8644 (10 micrometer), an activator of L-type Ca2+ channels and cyclopiazonic acid (10 micrometer), an inhibitor of cytoplasmic Ca2+-ATPase were also inhibited. However, S(-)-raclopride (1~10 micrometer), given into an adrenal vein for 60 min, enhanced the CA secretory responses evoked by ACh, high K+, DMPP and McN-A-343 only for the first period (4 min), although it alone has weak effect on CA secretion. Moreover, S(-)-raclopride (3.0 micrometer) in to an adrenal vein for 60 min also augmented the CA release evoked by BAY-K-8644 and cyclopiazonic acid only for the first period (4 min). However, after simultaneous perfusion of R-(-)-TNPA (30 micrometer) and S(-)-raclopride (3.0 micrometer), the inhibitory responses of R-(-)-TNPA (30 micrometer) on the CA secretion evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644, and cyclopiazonic acid were significantly reduced. Taken together, these experimental results suggest that R-(-)-TNPA greatly inhibits the CA secretion from the perfused rat adrenal medulla evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) and membrane depolarization, but S(-)-raclopride rather enhances the CA release by them. It seems that this inhibitory of R-(-)-TNPA may be mediated by stimulation of inhibitory dopaminergic D2 receptors located on the rat adrenomedullary chromaffin cells, while the facilitatory effect of S(-)-raclopride is due to the blockade of dopaminergic D2 receptors, which are relevant to extra- and intracellular calcium mobilization. Therefore, it is thought that dopaminergic D2 receptors may be involved in regulation of CA release in the rat adrenal medulla.
(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Adrenal Glands ; Adrenal Medulla* ; Animals ; Calcium ; Catecholamines ; Chromaffin Cells ; Cytoplasm ; Dimethylphenylpiperazinium Iodide ; Membranes ; Perfusion ; Rats* ; Veins

BACKGROUND: Vascular smooth muscle cells (VSMCs) proliferation is an important process in the pathogenesis of atherosclerosis. VSMCs proliferation is closedly related to the cytosolic calcium flux via L-type voltage dependent calcium channel. OBJECTIVES: To investigate the role of cytosolic Ca(2+) in the proliferation of VSMCs. METHODS: The proliferation of aortic vascular smooth muscle cells of rats(1% cholesterol diet fed rats and general diet fed ones), acquired by enzymatic method. Cell counting, and calcium agonists(Bay K 8644 10(-6)M) or calcium antagonists(verapamil 10(-6)M). Cytosolic calcium ion was measured with Fura 2 method. Calcium channel gene expresssion was detected with RT-PCR method. RESULTS: Masson Trichrome staining shows more disturbed cell lining, more VSMCs, more degenerated media, more collagen laydown, and more adventitial fat in the aorta of cholesterol-fed rats than in that of general diet-fed ones. VSMCs of cholesterol fed-rats were moreproliferated than those of general diet fed-ones. Bay K 8644 enhanced VSMCs proliferation of both groups. Verapamil blocked the incremental effects induced by Bay K 8644. Expression of calcium channel gene was enhanced by Bay K 8644 and was reversed by verapamil. CONCLUSION: The enhanced proliferation of atherosclerotic VSMCs is associated with the increment in cytosolic calcium, which is accomplshed through the expression of L-type voltage dependent calcium channel.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Animals ; Aorta* ; Atherosclerosis ; Calcium Channels ; Calcium* ; Cell Count ; Cholesterol* ; Collagen ; Cytosol* ; Diet ; Fura-2 ; Muscle, Smooth* ; Muscle, Smooth, Vascular ; Myocytes, Smooth Muscle* ; Rats* ; Verapamil

Background : Vascular smooth muscle cells(VSMCs) proliferation is an important process in the pathogenesis and progression of atherosclerosis, Calcium is considered an important regulator of cellular proliferation. The major mechanism regulating VSMC cytoplasmic Ca2+ activity are Ca2+ entry and extrusion across the plasmalemma and Ca2+ release and uptake by the sarcoplasmic reticulum. To investigate the role of cytosolic Ca2+ in the proliferaton of VSMCs, we studied the proliferation and the dynamics of cytosolic Ca2+ in VSMCs from nondiabetic rats. Methods : The proliferation of aortic vascular smooth muscle cells of rats, acquired by enzymatic method, was studied with MTT assay, and calcium agonists (Bay K 8644 10(-6)M) or calcium antagonists(verapamil 10(-6)M). Cytosolic Ca2+ was measured by Fura 2 method. Results : Bay K 8644 enhanced VSMCs proliferation. Verapamil blocked the incremental effect induced by Bay K 8644. In the presence of extracellular calcium ion, Bay K 8644 (10(-6)M) abolished the increase in [Ca2+]i induced by Bay K 8644 in the presence of 1mM extracellular calcium ion. Conclusion : The enhanced proliferation of VSMCs is associated with the increment in cytosolic calcium.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Animals ; Atherosclerosis ; Calcium ; Cell Proliferation ; Cytoplasm ; Cytosol* ; Fura-2 ; Muscle, Smooth, Vascular* ; Rats ; Sarcoplasmic Reticulum ; Verapamil

BACKGROUND: The proliferation of vascular smooth muscle cells(VSMCs) is an important process in the pathogenesis of atherosclerosis. VSMCs proliferation is closedly related to the cytosolic calcium flux via L-type voltage dependent calcium channel. OBJECTIVES: To investigate the role of cytosolic Ca2+ in the proliferation of VSMCs. METHODS: The proliferation of aortic vascular smooth muscle cells of streptozotocin induced diabetic rats, acquired by enzymatic method. Cell counting, and calcium agonists(Bay K 8644 10(-6)M) or calcium antagonists(verapamil 10(-6)M). Cytosolic calcium ion was measured with Fura 2 method. Calcium channel gene expression was detected with RT-PCR method. RESULTS: VSMCs of diabetic rats were more proliferated than those of nondiabetic ones. Bay K 8644 enhanced VSMCs proliferation of both groups. Verapamil blocked the incremental effects induced by Bay K 8644. Expression of calcium channel gene was enhanced by Bay K 8644 and was reversed by vera- pamil. CONCLUSION: The enhanced proliferation of VSMCs is associated with the increment in cytosolic calcium, which is accompli shed through the expression of L-type voltage dependent calcium channel.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Animals ; Aorta* ; Atherosclerosis ; Calcium ; Calcium Channels ; Cell Count ; Cytosol ; Fura-2 ; Gene Expression ; Muscle, Smooth, Vascular* ; Rats* ; Streptozocin ; Verapamil