The activation of Ca2+ entry through store-operated channels by agonists that deplete Ca2+ from the endoplasmic reticulum (ER) is a ubiquitous signaling mechanism, the molecular basis of which has remained elusive for the past two decades. Store-operated Ca2+-release-activated Ca2+ (CRAC) channels constitute the sole pathway for Ca2+ entry following antigen-receptor engagement. In a set of breakthrough studies over the past two years, stromal interaction molecule 1 (STIM1, the ER Ca2+ sensor) and Orai1 (a pore-forming subunit of the CRAC channel) have been identified. Here we review these recent studies and the insights they provide into the mechanism of store-operated Ca2+ channels (SOCCs).
Animals ; Calcium ; metabolism ; Calcium Channels ; metabolism ; Calcium Signaling ; drug effects ; Humans ; Membrane Proteins ; antagonists & inhibitors ; metabolism ; Protein Binding

AIMTo investigate the effects of 323-A and 323-B, two isomers extracted from the metabolites of cultured marine fungus, Halorosellinia oceanicum 323, on the contraction of isolated guinea pig ileum (GPI).

METHODSThe GPI contractions were recorded with a two-channel-physiological recorder with tension transducers. Cumulative dose-response curves of contractions of isolated GPI induced by histamine (Hist), acetylcholine (ACh) and potassium chloride (KCl) were constructed, then the influences of 323-A and 323-B on each curve were observed. Furthermore, possible mechanisms underlying effects of the two compounds were explored by analyzing their influences on the biphasic contractile response to ACh, with comparison of a calcium antagonist, verapamil (Ver).

RESULTSThe data indicated that both 323-A and 323-B inhibited the contractile actions of GPI triggered by Hist, ACh and KCl in a concentration-dependent manner, with pD2' values of 5.13, 4.97, 5.36 and 5.51, 5.56, 5.62, respectively. The initial phase component of the ACh-elicited contractions, in the absence of external Ca2+, was significantly reduced by 323-A, 323-B, as well as Ver, whereas the subsequent sustained tonic contractions induced by adding Ca2+ to the bath solution were almost unaffected.

CONCLUSIONThese results suggest that 323-A and 323-B have calcium antagonistic effects similar to that of Ver in mechanisms, and they might have potential to be developed as calcium antagonists.

Acetylcholine ; antagonists & inhibitors ; Animals ; Calcium ; antagonists & inhibitors ; Calcium Channel Blockers ; isolation & purification ; pharmacology ; Female ; Fungi ; chemistry ; Guinea Pigs ; Histamine Antagonists ; pharmacology ; Ileum ; drug effects ; physiology ; Male ; Muscle Contraction ; drug effects ; Muscle, Smooth ; drug effects ; Potassium Chloride ; antagonists & inhibitors

In order to elucidate mechanisms of Ca++ antagonistic action of kanamycin in the biological system, the effects of kanamycin on Ca++ transport in sarcoplasmic reticulum of rabbit skeletal muscle and liver mitochondria were studied. At the same time, the effect of the agent on Bowditch and Woodworth phenomena of rabbit heart as well as the superprecipitation of actomyosin isolated from rabbit skeletal muscle were studied. Since kanamycin inhibits the Bowditch staircase phenomena in rabbit cardiac muscle, it is speculated that kanamycin inhibits Ca++ influx across the cell membrane which is required for the muscular contraction. Kanamycin also inhibits the Woodworth staircase phenomena, indicating a decrease in size of the Ca++ pool in cardiac muscle which may be brought about by an inhibition of Ca++ transport in sarcoplasmic reticulum and mitochondria. Actually, kanamycin was found to inhibit both the activities of Ca++ activated adenosine triphosphatases (ATPase) and Ca++ transport in sarcoplasmic reticulum and mitochondria. Kanamycin also inhibits both the development of superprecipitation and the activity of Ca++activated ATPase of skeletal actomyosin in rabbits. From the results obtained above, it may be concluded that kanamycin possesses a Ca++ antagonistic action in the biological system.
Animal ; Calcium/antagonists & inhibitors* ; Kanamycin/pharmacology* ; Mitochondria, Liver/metabolism ; Muscles/metabolism ; Myocardium/metabolism ; Rabbits

Small conductance Ca(2+)-activated potassium channels (SK channels) distributing in the nervous system play an important role in learning, memory and synaptic plasticity. Most pharmacological properties of them are determined by short-chain scorpion toxins. Different from most voltage-gated potassium channels and large-conductance Ca(2+)-activated potassium channels, SK channels are only inhibited by a small quantity of scorpion toxins. Recently, a novel peptide screener in the extracellular pore entryway of SK channels was considered as the structural basis of toxin selective recognition. In this review, we summarized the unique interactions between scorpion toxins and SK channels, which is crucial not only in deep-researching for physiological function of SK channels, but also in developing drugs for SK channel-related diseases.
Animals ; Memory ; Neuronal Plasticity ; Scorpion Venoms ; chemistry ; Scorpions ; Small-Conductance Calcium-Activated Potassium Channels ; antagonists & inhibitors

AIMTo study the vasodilation effect of atropine and its mechanism.

METHODSIsometric tension was recorded in isolated rat super mesenteric arteries precontracted by noradrenaline (NE) to study the vasodilation effect of atropine, and to investigate the role of endothelial cell and vascular smooth muscle cell on vasodilation.

RESULTSAtropine was shown to significantly dilate the endothelium-intact and endothelium-denuded arteries precontracted by NE. Nomega-Nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhabitor), indomethacin (cyclooxygenase inhibitor), propranolol (general beta adrenoceptor antagonist) and glibenclamide (ATP sensitive potassium channel inhibitor) showed no effect on vasodilation of atropine. Atropine did not affect the concentration-contraction curve of K+. However, atropine suppressed the contraction induced by NE and CaCl2, but not that by caffeine in the Ca+ -free Krebs solution.

CONCLUSIONAtropine showed significant vasodilation effect which may derive, in part, from endothelium. Besides, atropine could inhibit the receptor-mediated Ca2+ -influx and Ca2+ -release, which was inferred to the mechanism of atropine on vasodilation.

Animals ; Atropine ; pharmacology ; Calcium ; metabolism ; Calcium Chloride ; antagonists & inhibitors ; Cyclooxygenase Inhibitors ; pharmacology ; Endothelial Cells ; physiology ; Female ; In Vitro Techniques ; Indomethacin ; antagonists & inhibitors ; Male ; Mesenteric Artery, Superior ; drug effects ; NG-Nitroarginine Methyl Ester ; antagonists & inhibitors ; Nitric Oxide Synthase ; antagonists & inhibitors ; Norepinephrine ; antagonists & inhibitors ; Potassium Chloride ; antagonists & inhibitors ; Rats ; Rats, Sprague-Dawley ; Vasodilation ; drug effects ; Vasodilator Agents ; pharmacology

This study examined whether propofol and aminophylline affect the mobilization of intracellular calcium in human umbilical vein endothelial cells. Intracellular calcium was measured using laser scanning confocal microscopy. Cultured and serum-starved cells on round coverslips were incubated with propofol or aminophylline for 30 min, and then stimulated with lysophosphatidic acid, propofol and aminophylline. The results were expressed as relative fluorescence intensity and fold stimulation. Propofol decreased the concentration of intracellular calcium, whereas aminophylline caused increased mobilization of intracellular calcium in a concentration-dependent manner. Propofol suppressed the lysophosphatidic acid-induced mobilization of intracellular calcium in a concentration-dependent manner. Propofol further prevented the aminophylline-induced increase of intracellular calcium at clinically relevant concentrations. However, aminophylline reversed the inhibitory effect of propofol on the elevation of intracellular calcium by lysophosphatidic acid. Our results suggest that propofol and aminophylline antagonize each other on the mobilization of intracellular calcium in human umbilical vein endothelial cells at clinically relevant concentrations. Serious consideration should be given to how this interaction affects mobilization of intracellular calcium when these two drugs are used together.
Aminophylline/*antagonists & inhibitors/pharmacology ; Anesthetics, Intravenous/*antagonists & inhibitors/pharmacology ; Bronchodilator Agents/*antagonists & inhibitors/pharmacology ; Calcium/*metabolism ; Cells, Cultured ; Endothelial Cells/*drug effects/metabolism ; Endothelium, Vascular/cytology ; Humans ; Lysophospholipids/pharmacology ; Microscopy, Confocal ; Propofol/*antagonists & inhibitors/pharmacology ; Umbilical Veins/cytology

OBJECTIVETo study the role of N-methyl-D-aspartate receptor and Ca(2+) in acute intoxicated encephalopathy induced by 1, 2-dichloroethane (1, 2-DCE) in vitro.

METHODSNeurocytes of new born rats were cultured in vitro, which were administered with different doses of 1, 2-DCE, and NMDAR and Ca(2+) antagonists including Ketamine and Nimodiping respectively. The cell morphologic structures were observed under light microscope, and its proliferation was detected by Cell Counting Kit-VIII.

RESULTS1, 2-DCE could damage the normal morphological structure of neurocytes: the cell body swelled and broke down, the karyon slurred or disappeared, the axone became shorten and thick, connection of neurocytes was reduced, the cell membrane was half-baked, injury of neurocytes became severer with the increase of the dose of 1, 2-DCE. There was no statistical difference in the proliferation of neurocytes between every 1, 2-DCE groups (P > 0.05), but there was significantly statistical difference between 1, 2-DCE groups, the control group, and the retarder groups (P < 0.01).

CONCLUSION1, 2-DCE can damage the normal morphological structure of neurocytes, and the damage will become severer with the increase of the dose of 1, 2-DCE. However, the cell morphologic structures and proliferation of antagonist groups are much better than those in the 1, 2-DCE groups.

Animals ; Calcium ; antagonists & inhibitors ; physiology ; Cells, Cultured ; Ethylene Dichlorides ; toxicity ; Neurons ; drug effects ; pathology ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; antagonists & inhibitors ; physiology

Recently several kinds of new antihypertensive agents were introduced. Diuretics such as indapamide, metyrazone and eprelerone have less side effects compared to thiazide, and have an effect in renal insufficiency. Carvedilol, combined alpha- and beta- adrenergic blocker, has a vasodilating property and an effect on heart failure. The lipid soluble third generation calcium antagonists such as amlodipine, lacidipine and lercardipine are slow onset and long acting and have less side effects, which provide continued effect even if daily doses are missed. Multiple angiotensin converting inhibitors and angiotensin receptor blockers, and the specific aldosterone antagonist eprenolone to block renin-angiotensin-aldosterone system are now available. Additionally new class antihypertensive drugs such as the vasopeptidase inhibitor, the endothelin receptor blocker and the renin inhibitor have been under investigation and shown favorable clinical results, and will be available for clinical use soon.
Adrenergic Antagonists ; Aldosterone ; Amlodipine ; Angiotensin Receptor Antagonists ; Angiotensins ; Antihypertensive Agents ; Calcium ; Diuretics ; Heart Failure ; Hypertension* ; Indapamide ; Receptors, Endothelin ; Renal Insufficiency ; Renin ; Renin-Angiotensin System

MTT analysis and intracellular calcium measurement by using confocal laser scanning microscopy were used to study the possible mechanism of protective effect of pituitary adenylate cyclase activating polypeptide 27 (PACAP27) from beta amyloid protein (Abeta)-induced neurotoxicity. The results showed that treatment with PACAP (less than 0.1 micromol/L) increased the survival and reproductive ability of neuro-2a cells and protected the neuro-2a cells from being injured by Abeta. The protective effect of PACAP27 was reversed by the competitive PACAP receptor antagonist PACAP6-27. An increase in intracellular calcium was observed when the cells were challenged with Abeta and PACAP. But the calcium increase induced by Abeta kept stable for a long time while PACAP caused a transient rise in intracellular calcium. The intracellular calcium increase induced by Abeta was blocked by pretreatment with PACAP for 10 min. It is suggested that the neuroprotective effect of PACAP against neuronal damage induced by Abeta may result from its role in inhibiting the sustained rise in intracellular calcium.
Amyloid beta-Peptides ; antagonists & inhibitors ; toxicity ; Calcium ; metabolism ; Calcium Channels ; metabolism ; Cell Line, Tumor ; Humans ; Neuroblastoma ; pathology ; Neuroprotective Agents ; pharmacology ; Pituitary Adenylate Cyclase-Activating Polypeptide ; pharmacology

We stimulated preadipocyte of mice with calcium acetate, p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580, the paralysors and excitomotors of calcium channel. Then we detected expression level of preadipocyte differentiation's marker genes and calcium signal related acceptor genes by real-time PCR, and determined intracellular free Ca2+ concentration ([Ca2+]i]) with Fura-2/AM, intracellular lipid accumulation by oil red O staining. Our aim was to investigate the potential mechanism between calcium signal and preadipocyte differentiation. The results indicated that the paralysors and excitomotors of calcium channel changed the expression level of lipoprotein lipase (LPL), peroxisome proliferators-activated receptor gamma (PPARgamma), fatty acid synthetase (FAS), and the lipid accumulation, markedly. Compared with exocellular Ca2+'s decrease, inhibited intracellular Ca2+'s liberation can promoted preadipocyte differentiation (P < 0.01), and compared with intracellular Ca2+'s increase, promoted exocellular Ca2+'s ingest inhibited preadipocyte differentiation (P < 0.01). SB203580 degraded [Ca2+]i, promoted differentiation marker genes' expression and lipid accumulation in preadipocyte (P < 0.01). But calcium signal didn't have effects to vitamin D receptor (VDR) and extracellular Ca2+-sensing receptor (CaSR)'s expression. It indicated that calcium signal may effect preadipocyte different and lipid accumulation by p38 MAPK pathway.
Adipocytes ; cytology ; Animals ; Calcium ; metabolism ; Calcium Signaling ; drug effects ; Cell Differentiation ; physiology ; Cells, Cultured ; Imidazoles ; pharmacology ; Lipids ; biosynthesis ; Mice ; Pyridines ; pharmacology ; p38 Mitogen-Activated Protein Kinases ; antagonists & inhibitors