Resveratrol inhibits Ca

BACKGROUND@#Resveratrol has been shown to inhibit platelet aggregation. However, the mechanism for this action of resveratrol remains to be clarified. The purpose of this study was to elucidate the Ca@*METHODS@#Ca@*RESULTS@#Thapsigargin-induced Ca@*CONCLUSIONS@#The results suggest that resveratrol inhibits thrombin-induced platelet aggregation through decreasing Ca

Effects of cardiac remodeling on atrial arrhythmogenesis in aged rabbit left atrium / 中国病理生理杂志

AIM: To investigate the effects of myocardial remodeling of aged left atrium (LA) on atrial ar-rhythmogenesis in rabbits .METHODS:The male New Zealand rabbits were divided into young LA and aged LA groups . By observing the changes of monophasic action potential ( MAP) and burst-pacing in LA of the rabbits in vivo, the main cardioelectrophysiological parameters such as resting membrane potential ( RMP) , action potential amplitude ( APA) , ma-ximum rise veloctiy of action potential (dv/dtmax), plateau potential and action potential duration at 30%, 50%and 90%( APD30 , APD50 and APD90 ) , as well as the inducibility and duration of atrial arrhythmias were recorded .L-type calcium current (ICa,L) was analyzed via whole-cell patch-clamp technique in enzymatically dissociated single rabbit LA myocytes . The myocardial collagen content was quantified after Masson staining , and the ultrastructure of the LA cells was observed under scanning electron microscope .The expression of Cav 1.2 in LA tissue of the 2 groups was detected by Western blot . RESULTS:Compared with young LA group , dv/dtmax and plateau potential were significantly decreased , APD30 and APD50 were shortened, and APD90 was notably prolongated in aged LA group (P<0.01).The inducibility or duration of atrial arrhythmias was severely increased or prolongated in aged LA group (P<0.01).With voltage clamp model, the den-sity of ICa,L in aged LA group was significantly decreased , and current-voltage curve was notably moved upward compared with young LA group.When the clamp potential was +20 mV, the density of ICa,L was notably modified from (11.72 ± 1.39) pA/pF in young LA group to (6.08 ±0.98) pA/pF in aged LA group ( P<0.01).Compared with young LA group, the protein level of collagen was significantly increased (P<0.01), and the arrange of atrial myocytes was irregular in LA of rabbits in aged LA group .The atrial myocytes of the LA wall in aged LA group exhibited abnormal ultrastructural alterations , such as karyopyknosis , irregular and swelling mitochondria with the presence of vacuoles , and mild and severe sarcomere degeneration .Compared with those in LA tissues of young rabbits , the expression levels of Cav 1.2 in the LA tis-sues of aged rabbits were severely reduced (P<0.01), and had a significant positive correlation with the reduction of ICa,L (r=0.83, P<0.01).CONCLUSION:The pathophysiological characteristics of aged LA are significantly altered , and might contribute to vulnerability and susceptibility of occurrence of atrial fibillation in aged rabbits .The mechanisms might completely attribute to the notable reduction of ICa,L , abnormal alterations of ultrastructures and obvious decrease in the ex-pression of Cav1.2 in the aged LA of aged rabbits .

Vasorelaxant effect of novel Rho-kinase inhibitors on isolated thoracic aorta rings and underlying mechanisms / 中国药理学通报

Aim To evaluate the vasorelaxant effect of two new chemical entities, J35242 and J35243, on iso-lated rat thoracic aorta rings as Rho-kinase inhibitors, and further to explore the underlying mechanisms of these two compounds. Methods Isolated rat thoracic aorta rings pre-contracted by KCl or norepinephrine ( NE) were used to evaluate the vasodilatory effect of J35242 and J35243 . Through the interventions of sev-eral tool drugs, the mechanisms of compounds concern-ing endothelium, K+ channels and Ca2+ were studied. Results J35242 and J35243 showed potent relaxant effect on both KCl and NE pre-contracted vessels, and exhibited partial endothelium dependency. L-NAME and Methylene Blue( MB) could influence the relaxant effect of these compounds. Meanwhile, the compounds could inhibit intracellular Ca2+ release and extracellu-lar Ca2+ influx, which indicated that the compounds might block the calcium channels to relax the vessels. In addition, the two compounds probably did not dilate the aorta rings through opening potassium channels. Conclusions J35242 and J35243 have vasorelaxant effects on vessels in vitro and the potency of J35242 is stronger than that of J35243 . The underlying mecha-nisms might be endothelium-dependent. Also the com-pounds might block Ca2+ channels, lowering intracel-lular Ca2+ concentration to relax the vessels.

Effect of SKF96365 and NiCl2 on cyclopiazonic acid induced intracellular calcium cation concentration increase in rat distal pulmonary arterial smooth muscle cells / 重庆医学

Objective To study the effect of SKF96365 and NiCl2 on cyclopiazonic acid (CPA) induced intracellular calcium cation concentration ([Ca2+ ]i ) change in rat distal pulmonary arterial smooth muscle cells (PASMC) .Methods The rat distal PASMC were isolated and cultured .The effects of CPA ,SKF96365 and NiCl2 on [Ca2+ ]i in PASMC were tested by fluorescence microscope and InCyte [Ca2+ ]i measurement system .Results PASMC were incubated with Ca2+‐free Krebs solution containing 5μmol/L nifedipine ,10 μmol/L CPA caused a small transient increase in [Ca2+ ]i ;after restoration of extracellular Ca2+ to 2 .5 mmol/L ,10 μmol/L CPA caused marked increases in [Ca2+ ]i in PASMC incubated with Krebs solution containing 5 μmol/L nife‐dipine .Both 50 μmol/L SKF96365 and 500 μmol/L NiCl2 distinctly attenuated the increases in [Ca2+ ]i caused by 10 μmol/L CPA in PASMC .However ,neither 50 μmol/L SKF96365 nor 500 μmol/L NiCl2 affected the increases in [Ca2+ ]i caused by 60 mmol/L KCl in PASMC .Conclusion CPA induced increases in [Ca2+ ]i may related to Ca2+ release from sarcoplasmic reticulum and the in‐flux of Ca2+ through store‐operated Ca2+ channels (SOCC) in rat distal PASMC .Both SKF96365 and NiCl2 could selectively block SOCC and attenuated the influx of Ca2+ through SOCC in PASMC .

Effect of Acute Hypoxia on Cyclopiazonic Acid Induced Intracellular Calcium Cation Enhancement in Rat Distal Pulmonary Venous Smooth Muscle Cells / 中国循环杂志

Objective: To study the effect and the mechanism of acute hypoxia on Ca2+-ATPase inhibitor, cyclopiazonic acid (CPA) induced intracellular calcium cation enhancement in rat distal pulmonary venous smooth muscle cells (PVSMC) . Methods: The PVSMC were isolated from 6 male SD rats and the cells were cultured for further experiment. Enhancing effects of CPA, acute hypoxia (4% O2) on [Ca2+]i in distal PVSMC and the interventional effects of 2 store-operated Ca2+ channels (SOCC) inhibitors, NiCl2 and SKF96365 on [Ca2+]i in distal PVSMC were tested by lfuorescence microscope and intracellular [Ca2+] examining system. Results: When PVSMC were perfused with Ca2+-free Krebs solution containing 5 μmol/L nifedipine, 10 μmol/L CPA caused a slight elevation of [Ca2+]i, and acute hypoxia obviously enhanced the [Ca2+]i in PVSMC. When restoration of extracellular [Ca2+] to 2.5 mmol/L, 10 μmol/L CPA caused signiifcant elevation of [Ca2+]i, and acute hypoxia obviously enhanced [Ca2+]i induced by CPA in PVSMC. The SOCC inhibitors, NiCl2 (500 μmol/L) and SKF96365 (50 μmol/L) distinctively attenuated the elevation of [Ca2+]i by hypoxia and CPA. However, NiCl2 and SKF96365 had no effect on high potassium (60 mmol/L KCl Krebs solution) induced elevation of [Ca2+]i in distal PVSMC. Conclusion: Acute hypoxia enhanced the elevation of [Ca2+]i induced by CPA; such effect could be selectively blocked by SOCC inhibitor which indicated that acute hypoxia could enhance the activity of SOCC in rat distal PVSMC.

Vasorelaxant effect of Rho kinase inhibitor DL0805-0 on isolated rat aortic rings and its underlying mechanisms / 中国药理学通报

Aim To investigate the in vitro vasorelax-ant effect of DL0805-0, a Rho kinase inhibitor, on iso-lated rat thoracic aorta and explore its underlying mechanism. Methods Tension was measured to eval-uate the vasorelaxant effect of DL0805-0 on rat endo-thelium-intact and endothelium-denuded thoracic aorta rings. Rho kinase inhibitor fasudil, nitric oxide syn-thase inhibitor Nω-nitro-L-arginine methyl ester ( L-NAME), guanylate cyclase inhibitor methylene blue, cyclooxygenase inhibitor indomethacin, calcium-activa-ted potassium channel blocker tetraethyl ammonium ( TEA ) , ATP-sensitive potassium channel blocker glibenclamide and voltage-dependent potassium chan-nel blocker 4-aminopyridine ( 4-AP ) were used to il-lustrate the mechanisms of vasorelaxant effect of DL0805-0 . Results DL0805-0 exerted vasorelaxation in a dose-dependent manner in KCl (60 mmol·L-1 ) or NE ( 0. 1 μmol · L-1 ) -induced contraction. DL0805-0-induced vasorelaxation was significantly re-duced by L-NAME. However, methylene blue and in-domethacin did not significantly affect vasorelaxation of DL0805-0. In endothelium-denuded rings, TEA re-markably attenuated the vasorelaxant effect of DL0805-0 , while glibenclamide and 4-AP did not affect vasore laxation of DL0805-0 significantly. DL0805-0 also re-duced NE-induced transient contraction and inhibited contraction induced by increasing extracellular calci-um. Conclusion These results suggest that DL0805-0 induces vasorelaxation through an endothelium-depend-ent pathway. The opening of calcium-activated K+channels and blocking of Ca2+ channels in vascular smooth muscle cells may be one of the mechanisms of DL0805-0-induced vasorelaxation.

Erythroxylum pungens elicits vasorelaxation by reducing intracellular calcium concentration in vascular smooth muscle cells of rats

The cardiovascular effects elicited by the ethanolic extract obtained from the roots of Erythroxylum pungens O.E. Schulz, Erythroxylaceae (EEEP) and the vasorelaxant effect induced by its main tropane alkaloid (pungencine) were investigated. In normotensive rats, administration of EEEP (1, 10, 30 and 60 mg/kg i.v., randomly) produced dose-dependent hypotension (-2±1, -7±0.5 -17.6±1, -24±1 Δ mmHg, n=5) followed by tachycardia (3±0.5, 7±2, 7.1±1, 10±5 Δ bpm, n=5). In intact phenylephrine (Phe, 10 µM)-pre-contracted rings, EEEP (0.01-500 µg/mL) induced concentration-dependent vasorelaxation (EC50 13.7±5.5 µg/mL, Maximal Response= 92±2.6%), and this effect was unchanged after the removal of the vascular endothelium (EC50 27.2±4.7 µg/ml, Maximal Response= 88.3±3.3 %). In KCl (80 mM)-pre-contracted-endothelium-denuded rings, EEEP elicited concentration-dependent relaxation (EC50= 128.2±11.2 µg/mL, Maximal Response 76.8±3.4%). Vasorelaxation has also been achieved with tonic contractions evoked by the L-type Ca2+ channel agonist Bay K 8644 (EC50 80.2±9.1 µg/mL, Maximal Response 86.3±8.3%). In addition, in a depolarizing medium, EEEP inhibited CaCl2 (30-500 µg/mL) induced contractions and caused a concentration-dependent rightward shift of the relaxation curves. Lastly, the tropane alkaloid pungencine caused vasorelaxation in mesenteric arteries resembling to the EEEP responses. These results suggests that EEEP induces hypotension and vasorelaxation, at least in part, due to the reduction in [Ca2+]i in vascular smooth muscle cells.

Octyl Gallate Inhibits ATP-induced Intracellular Calcium Increase in PC12 Cells by Inhibiting Multiple Pathways

Phenolic compounds affect intracellular free Ca2+ concentration ([Ca2+]i) signaling. The study examined whether the simple phenolic compound octyl gallate affects ATP-induced Ca2+ signaling in PC12 cells using fura-2-based digital Ca2+ imaging and whole-cell patch clamping. Treatment with ATP (100 micrometer) for 90 s induced increases in [Ca2+]i in PC12 cells. Pretreatment with octyl gallate (100 nM to 20 micrometer) for 10 min inhibited the ATP-induced [Ca2+]i response in a concentration-dependent manner (IC50=2.84 micrometer). Treatment with octyl gallate (3 micrometer) for 10 min significantly inhibited the ATP-induced response following the removal of extracellular Ca2+ with nominally Ca2+-free HEPES HBSS or depletion of intracellular Ca2+ stores with thapsigargin (1 micrometer). Treatment for 10 min with the L-type Ca2+ channel antagonist nimodipine (1 micrometer) significantly inhibited the ATP-induced [Ca2+]i increase, and treatment with octyl gallate further inhibited the ATP-induced response. Treatment with octyl gallate significantly inhibited the [Ca2+]i increase induced by 50 mM KCl. Pretreatment with protein kinase C inhibitors staurosporin (100 nM) and GF109203X (300 nM), or the tyrosine kinase inhibitor genistein (50 micrometer) did not significantly affect the inhibitory effects of octyl gallate on the ATP-induced response. Treatment with octyl gallate markedly inhibited the ATP-induced currents. Therefore, we conclude that octyl gallate inhibits ATP-induced [Ca2+]i increase in PC12 cells by inhibiting both non-selective P2X receptor-mediated influx of Ca2+ from extracellular space and P2Y receptor-induced release of Ca2+ from intracellular stores in protein kinase-independent manner. In addition, octyl gallate inhibits the ATP-induced Ca2+ responses by inhibiting the secondary activation of voltage-gated Ca2+ channels.

Nicotine-evoked cytosolic Ca2+ increase and cell depolarization in capillary endothelial cells of the bovine adrenal medulla

Endothelial cells are directly involved in many functions of the cardiovascular system by regulating blood flow and blood pressure through Ca2+ dependent exocitosis of vasoactive compounds. Using the Ca2+ indicator Fluo-3 and the patch-clamp technique, we show that bovine adrenal medulla capillary endothelial cells (B AMCECs) respond to acetylcholine (ACh) with a cytosolic Ca2+ increase and depolarization of the membrane potential (20.3±0.9 mV; n=23). The increase in cytosolic Ca2+ induced by 10µM ACh was mimicked by the same concentration of nicotine but not by muscarine and was blocked by 100 µM of hexamethonium. On the other hand, the increase in cytosolic Ca2+ could be depressed by nifedipine (0.01 -100 µM) or withdrawal of extracellular Ca2+. Taken together, these results give evidence for functional nicotinic receptors (nAChRs) in capillary endothelial cells of the adrenal medulla. It suggests that nAChRs in B AMCECs may be involved in the regulation of the adrenal gland's microcirculation by depolarizing the membrane potential, leading to the opening of voltage-activated Ca2+ channels, influx of external Ca2+ and liberation of vasoactive compounds.

Influence of omega-Conotoxin GVIA, Nifedipine and Cilnidipine on Catecholamine Release in the Rat Adrenal Medulla

The present study was designed to establish comparatively the inhibitory effects of cilnidipine (CNP), nifedipine (NIF), and omega-conotoxin GVIA (CTX) on the release of CA evoked by cholinergic stimulation and membrane depolarization from the isolated perfused model of the rat adrenal medulla. CNP (3 micrometer), NIF (3 micrometer), and CTX (3 micrometer) perfused into an adrenal vein for 60 min produced greatly inhibition in CA secretory responses evoked by ACh (5.32 x 10(-3) M), DMPP (10(-4) M for 2 min), McN-A-343 (10(-4) M for 2 min), high K+ (5.6 x 10(-2) M), Bay-K-8644 (10(-5) M), and cyclopiazonic acid (10(-5) M), respectively. For the CA release evoked by ACh and Bay-K-8644, the following rank order of potency was obtained: CNP > NIF > CTX. The rank order for the CA release evoked by McN-A-343 and cyclopiazonic acid was CNP > NIF > CTX. Also, the rank orders for high K+ and for DMPP were NIF > CTX > CNP and NIF > CNP > CTX, respectively. Taken together, these results demonstrate that all voltage-dependent Ca2+ channels (VDCCs) blockers of cilnidipine, nifedipine, and omega-conotoxin GVIA inhibit greatly the CA release evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors and the membrane depolarization without affecting the basal release from the isolated perfused rat adrenal gland. It seems likely that the inhibitory effects of cilnidipine, nifedipine, and omega-conotoxin GVIA are mediated by the blockade of both L- and N-type, L-type only, and N-type only VDCCs located on the rat adrenomedullary chromaffin cells, respectively, which are relevant to Ca2+ mobilization. It is also suggested that N-type VDCCs play an important role in the rat adrenomedullary CA secretion, in addition to L-type VDCCs.

The Effect of Tyrosine Kinase Inhibitors on the L-type Calcium Current in Rat Basilar Smooth Muscle Cells

OBJECTIVE: Tyrosine kinase inhibitors may be useful in the management of cerebral vasospasm. It has not yet been reported whether L-type Ca2+ channels play a role in tyrosine kinase inhibitors-induced vascular relaxation of cerebral artery. This study was undertaken to clarify the role of L-type Ca2+ channels in tyrosine kinase inhibitors-induced vascular relaxation, and to investigate the effect of tyrosine kinase inhibitors on L-type Ca2+ channels currents in freshly isolated smooth muscle cells from rat basilar artery. METHODS: The isolation of rat basilar smooth muscle cells was performed by special techniques. The whole cell currents were recorded by whole cell patch clamp technique in freshly isolated smooth muscle cells from rat basilar artery. RESULTS: Patch clamp studies revealed a whole-cell current which resembles the L-type Ca2+ current reported by others. The amplitude of this current was decreased by nimodipine and increased by Bay K 8644. Genistein(n=5), tyrphostin A-23(n=3), A-25(n=6) 30micrometer reduced the amplitude of the L-type Ca2+ channel current in whole cell mode. In contrast, diadzein 30 micrometer (n=3), inactive analogue of genistein, did not decrease the amplitude of the L-type Ca2+ channels current. CONCLUSION: These results suggest that tyrosine kinase inhibitors such as genistein, tyrphostin A-23, A-25 may relax cerebral vessel through decreasing level of intracellular calcium, [Ca2+]i, by inhibition of L-type Ca2+ channel.

The effects of a sodium and a calcium channel blocker on lethality of mice injected with the yellow scorpion (Leiurus quinquestriatus) venom

Scorpion venom toxins generally produce similar effects by mainly acting on sodium channels, and to a lesser extent, on potassium, calcium, and chloride channels. This leads to increased release of neurotransmitters and mediators, resulting in a cascade of pathological events, involving the central nervous system, the autonomic nervous system, the cardiovascular and the respiratory system, eventually leading to death. The objective of this paper was to discover whether a sodium channel blocker, lidocaine, or a calcium channel blocker, verapamil, would prolong the survival of mice injected with the venom from the common yellow scorpion Leiurus quinquestriatus quinquestriatus (LQQ). For this purpose, mice were divided into 2 groups, each injected with a different venom dose (250 or 300 µg.kg-1, s.c.). Subgroups (n=10) from each group were given venom alone; different doses of lidocaine (4, 10, 15, or 20 mg.kg-1); or several doses of verapamil (0.01, 0.03, 0.1, 0.3, or 1 mg.kg-1). All doses of lidocaine and verapamil were intravenously administered 3 minutes before, 1, 5, and 15 minutes after venom injection. Percent surviving after 24 hours was recorded in addition to the time of death. In general, lidocaine significantly prolonged survival at the dose of 10 mg.kg-1 (P<0.05 and P<0.01, versus low and high dose of venom, respectively) or 15 mg.kg-1 (P<0.01 and P<0.001, versus low and high dose of venom, respectively; Covariance Wilcoxon survival statistics), especially when injected before the venom or in the early stages of envenomation. On the other hand, in all doses administered, verapamil was either toxic or showed non-significant results. Lidocaine, the sodium channel blocker, appears to play an important role in the protection from lethality of mice injected with LQQ venom, and significantly prolonged the survival time of mice whether injected before or in the early stages of envenomation.(AU)

Ca2+-induced Ca2+ Release from Sarcoplasmic Reticulum Negatively Regulates Myocytic ANP Release in Beating Rabbit Atria

It is not clear whether Ca2+-induced Ca2+ release from the sarcoplasmic reticulum (SR) is involved in the regulation of atrial natriuretic peptide (ANP) release. Previously, we have shown that nifedipine increased ANP release, indicating that Ca2+ entry via voltage-gated L-type Ca2+ channel activation decreases ANP release. The purpose of the present study was two-fold: to define the role of SR Ca2+ release in the regulation of ANP release and whether Ca2+ entry via L-type Ca2+ channel is prerequisite for the SR-related effect on ANP release. Experiments were performed in perfused beating rabbit atria. Ryanodine, an inhibitor of SR Ca2+ release, increased atrial myocytic ANP release (8.69+/-3.05, 19.55+/-1.09, 27.31+/-3.51, and 18.91+/-4.76% for 1, 2, 3, and 6microM ryanodine, respectively; all P< 1) with concomitant decrease in atrial stroke volume and pulse pressure in a dose-dependent manner. In the presence of thapsigargin, an inhibitor of SR Ca2+ pump, ryanodine-induced increase in ANP release was not observed. Thapsigargin attenuated ryanodine-induced decrease in atrial dynamic changes. Blockade of L-type Ca2+ channel with nifedipine abolished ryanodine-induced increase in ANP release (0.69+/-5.58% vs. 27.31+/-3.51%; P< 0.001). In the presence of thapsigargin and ryanodine, nifedipine increased ANP release and decreased atrial dynamics. These data suggest that Ca2+-induced Ca2+ release from the SR is inversely involved in the regulation of atrial myocytic ANP release.

Efffects of Fluoxetine on ATP-induced Calcium Signaling in PC12 Cells

Fluoxetine, a widely used anti-depressant compound, has several additional effects, including blockade of voltage-gated ion channels. We examined whether fluoxetine affects ATP-induced calcium signaling in PC12 cells by using fura-2-based digital calcium imaging and assay for [3H]-inositol phosphates (IPs). Treatment with ATP (100microM) for 2 min induced [Ca2+]i increases. The ATP-induced [Ca2+]i increases were significantly decreased by removal of extracellular Ca2+ and treatment with the inhibitor of endoplasmic reticulum Ca2+ ATPase thapsigargin (1microM). Treatment with fluoxetine for 5 min blocked the ATP-induced [Ca2+]i increase concentration-dependently. Treatment with fluoxetine (30microM) for 5 min blocked the ATP-induced [Ca2+]i increase following removal of extracellular Ca2+ and depletion of intracellular Ca2+ stores. While treatment with the L-type Ca2+ channel antagonist nimodipine for 10 min inhibited the ATP-induced [Ca2+]i increases significantly, treatment with fluoxetine alone blocked the ATP-induced responses. Treatment with fluoxetine also inhibited the 50 mM K+-induced [Ca2+]i increases completely. However, treatment with fluoxetine did not inhibit the ATP-induced [3H]-IPs formation. Collectively, we conclude that fluoxetine inhibits ATP-induced [Ca2+]i increases in PC12 cells by inhibiting both an influx of extracellular Ca2+ and a release of Ca2+ from intracellular stores without affecting IPs formation.

Molecular identification of Ca(2+)channels in human sperm

The acrosome reaction is a Ca(2+)-dependent exocytotic process that is a prerequisite step for fertilization. External calcium entry through voltage-activated Ca(2+)channels is known to be essential in inducing the acrosome reaction of mammalian spermatozoa. Due to their complex geometry, however, electrophysiological identification of sperm Ca(2+)channels has been limited. Here we identified Ca(2+)channel mRNAs expressed in motile human sperm using RT-PCR and their levels were compared using RNase protection assays. L-type, non- L-type, and T-type Ca(2+)channel mRNAs were detected by RT-PCR using degenerate primers. Cloning and sequencing of the PCR products revealed alpha1B, alpha1C, alpha1E, alpha1G, and alpha1H sequences. RT-PCR using specific primers repeatedly detected alpha1B, alpha1C, alpha1E, alpha1G, and alpha1H mRNAs, and additionally alpha1I mRNA. But alpha1A and alpha1D messages were not detected. Relative expression levels of the detected Ca(2+)channel subtypes were compared by RNase protection assays. The abundance of detected mRNA messages was in the following order: alpha1H> or =alpha1G> or =alpha1E> or =alpha1B>alpha1C>alpha1I. These findings indicated that human motile sperm express multiple voltage-activated Ca(2+)channel RNAs among which T-type and non-L-type channel messages are likely to be predominantly expressed. Based on their relative expression levels, we propose that not only T-type but also non-L-type calcium channels may be major gates for the external calcium influx, required for the acrosome reaction.

The Effect of Papaverine on L-Type Ca2+ Current in Rat Basilar Smooth Muscle Cells

OBJECTIVE: Papaverine has been used to manage vasospasm after subarachnoid hemorrhage. However, its mechanism for cerebrovascular smooth muscle are still not clear. This study was undertaken to investigate the effect of papaverine on L-type Ca2+ channels directly by using patch clamp techniques in freshly isolated single smooth muscle cells from rat basilar artery. METHODS: Whole-cell patch clamp technique was used for measuring the amplitude of L-type Ca2+ current. Papaverine was added to the bath solution. RESULTS: Patch clamp studies revealed a whole-cell current which resembles the L-type Ca2+ current reported by others. The amplitude of this current was decreased by nimodipidine and increased by Bay K 8644. Papaverine 100 micro M reduced the amplitude of the L-type Ca2+ channel current. CONCLUSION: We can conclude that papaverine may relax cerebral vessel through decreasing level of intracellular calcium, [Ca2+]i, by inhibition of L-type Ca2+ channel.

Effects of chloride channel blockers on KCl and 5-HT-induced contractile response at rabbit basilar artery rings / 中国药理学通报

AIM: To study the effects of different kinds of chloride channel blockers on KCl and 5-HT-induced contractile responses in cerebrovascular smooth muscle. METHOD: The tension of rabbit basilar artery rings was measured. RESULTS: 1 DIDS, furosemide and NPPB inhibited the responses to KCl and 5-HT in a concentration- dependent manner. The effects of DIDS, furosemide and NPPB on the response to 5-HT were stronger than that to KCl. 2 When SK&F 96365 evoked a maximum inhibitory effect on 5-HT-induced response, subsequent additions of DIDS, furosemide and NPPB could further produced vascular relaxation. CONCLUSION: The chloride channel participates KCl and 5-HT-induced contractile responses in cerebral basilar artery.

Effect of Ca2+-channel Blockers on Norepinephrine Release in the Rat Hippocampal Slice and Synaptosome

The aim of this study was to investigate the role of Ca2+-channel blockers in norepinephrine (NE) release from rat hippocampus. Slices and synaptosomes were incubated with [3H]-NE and the releases of the labelled products were evoked by 25 mM KCl stimulation. Nifedipine, diltiazem, nicardipine, flunarizine and pimozide did not affect the evoked and basal release of NE in the slice. But, diltiazem, nicardipine and flunarizine decreased the evoked NE release with a dose-related manner without any change of the basal release from synaptosomes. Also, a large dose of pimozide produced modest decrement of NE release. omega-conotoxin (CTx) GVIA decreased the evoked NE release in a dose-dependent manner without changing the basal release. And omega-CTxMVIIC decreased the evoked NE release in the synaoptosomes without any effect in the slice, but the effect of decrement was far less than that of omega-CTxGVIA. In interaction experiments with omega-CTxGVIA, omega-CTxMVIIC slightly potentiated the effect of omega-CTxGVIA on NE release in the slice and synaptosomal preparations. These results suggest that the NE release in the rat hippocampus is mediated mainly by N-type Ca2+-channels, and that other types such as L-, T- and/or P/Q-type Ca2+-channels could also be participate in this process.

Modulation of L-type Ca2+ channel currents by various protein kinase activators and inhibitors in rat clonal pituitary GH3 cell line

L-type Ca2+ channels play an important role in regulating cytosolic Ca2+ and thereby regulating hormone secretions in neuroendocrine cells. Since hormone secretions are also regulated by various kinds of protein kinases, we investigated the role of some kinase activators and inhibitors in the regulation of the L-type Ca2+ channel currents in rat pituitary GH3 cells using the patch-clamp technique. Phorbol 12,13-dibutyrate (PDBu), a protein kinase C (PKC) activator, and vanadate, a protein tyrosine phosphatase (PTP) inhibitor, increased the Ba2+ current through the L-type Ca2+ channels. In contrast, bisindolylmaleimide I (BIM I), a PKC inhibitor, and genistein, a protein tyrosine kinase (PTK) inhibitor, suppressed the Ba2+ currents. Forskolin, an adenylate cyclase activator, and isobutyl methylxanthine (IBMX), a non-specific phosphodiesterase inhibitor, reduced Ba2+ currents. The above results show that the L-type Ca2+ channels are activated by PKC and PTK, and inhibited by elevation of cyclic nucleotides such as cAMP. From these results, it is suggested that the regulation of hormone secretion by various kinase activity in GH3 cells may be attributable, at least in part, to their effect on L-type Ca2+ channels.

Effects of chloride channel blockers on KCl and 5-HT-induced contractile response at rabbit basilar artery rings / 中国药理学通报

AIM To study the effects of different kinds of chloride channel blockers on KCl and 5 HT induced contractile responses in cerebrovascular smooth muscle. METHOD The tension of rabbit basilar artery rings was measured. RESULTS ① DIDS, furosemide and NPPB inhibited the responses to KCl and 5 HT in a concentration dependent manner. The effects of DIDS, furosemide and NPPB on the response to 5 HT were stronger than that to KCl. ②When SK&F 96365 evoked a maximum inhibitory effect on 5 HT induced response, subsequent additions of DIDS, furosemide and NPPB could further produced vascular relaxation. CONCLUSION The chloride channel participates KCl and 5 HT induced contractile responses in cerebral basilar artery.