Ginseng saponins induce store-operated calcium entry in Xenopus oocytes

Ginseng gintonin, aging societies, and geriatric brain diseases

BACKGROUND

A dramatic increase in aging populations and low birth rates rapidly drive aging societies and increase aging-associated neurodegenerative diseases. However, functional food or medicinal formulations to prevent geriatric brain disorders are not readily available. Panax ginseng is a candidate, since ginseng has long-been consumed as a rejuvenating agent. However, the underlying molecular mechanisms and the components of ginseng that are responsible for brain rejuvenation and human longevity are unknown. Accumulating evidence shows that gintonin is a candidate for the anti-aging ingredient of ginseng, especially in brain senescence.

METHODS

Gintonin, a glycolipoprotein complex, contains three lipid-derived G protein-coupled receptor ligands: lysophosphatidic acids (LPAs), lysophosphatidylinositols (LPIs), and linoleic acid (LA). LPA, LPI, and LA act on six LPA receptor subtypes, GPR55, and GPR40, respectively. These G protein-coupled receptors are distributed within the nervous and non-nervous systems of the human body.

RESULTS

Gintonin-enriched fraction (GEF) exhibits anti-brain senescence and effects against disorders such as Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD). Oral administration of gintonin in animal models of d-galactose-induced brain aging, AD, HD, and PD restored cognitive and motor functions. The underlying molecular mechanisms of gintonin-mediated anti-brain aging and anti-neurodegenerative diseases include neurogenesis, autophagy stimulation, anti-apoptosis, anti-oxidative stress, and anti-inflammatory activities. This review describes the characteristics of gintonin and GEF, and how gintonin exerts its effects on brain aging and brain associated-neurodegenerative diseases.

CONCLUSION

Finally, we describe how GEF can be applied to improve the quality of life of senior citizens in aging societies.

Structural-Activity Relationship of Ginsenosides from Steamed Ginseng in the Treatment of Erectile Dysfunction

Ginseng has been reported to have diverse pharmacological effects. One of the therapeutic claims for ginseng is to enhance sexual function. Ginsenosides are considered as the major active constituents. A steaming process can alter the ginsenoside profile of ginseng products. The structure-function relationship of ginsenosides in the treatment of erectile dysfunction (ED) has not been investigated yet. In this work, 15 different processed ginsengs are produced by steaming, and 13 major ginsensosides are quantified by liquid chromatography with UV detection, including Rg1, Re, Rf, Rb1, Rc, Rb2, Rf, Rk3, Rh4, 20S-Rg3, 20R-Rg3, Rk1, and Rg5. Their anti-ED activities are screened using hydrocortisone-induced mice model (Kidney Yang Deficiency Syndrome in Chinese Medicine) and primary corpus cavernosum smooth muscle cells (CCSMCs). A processed ginseng with steaming treatment at 120[Formula: see text]C for 4[Formula: see text]h and five times possesses abundant ginsenosides Rk1, Rk3, Rh4 and Rg5 transformed via deglycosylation and dehydroxylation, and produces optimal activity against ED. The number of sugar molecules, structure of hydroxyl groups and stereoselectivity in ginsenosides affect their anti-ED activity. Among the 13 ginsenosides, Rk1, Rk3, Rh4 and Rg5 are the most efficient in decreasing intracellular calcium levels by inhibiting phosphodiesterase 5A (PDE5A) to reduce the degradation of cyclic guanosine monophosphate (cGMP) in CCSMCs. Rg5 also restrain hypoxia inducible factor-1[Formula: see text] (HIF-1[Formula: see text] expression in hypoxia state, and increase endothelial nitric oxide synthase (eNOS) expression in isolated rat cavernous tissue. These observations suggest a role for steamed ginseng containing two pairs of geometric isomers (i.e., Rk1/Rg5 and Rk3/Rh4) in the treatment of ED.

A Novel Korean Red Ginseng Compound Gintonin Inhibited Inflammation by MAPK and NF-κB Pathways and Recovered the Levels of mir-34a and mir-93 in RAW 264.7 Cells

The beneficial health promoting effects of ginseng from vitalizing the body to enhancing long life have been well explored very rapidly in the past few years. Up till now many ginsenosides have been discovered for their marvelous therapeutic effects. However during past three years, a novel ginseng compound has been discovered, called gintonin, that differs from other ginsenosides on the basis of its signal transduction and chemical nature. Gintonin has been widely studied for its anti-Alzheimer's disease activities and other neuropathies. However, its anti-inflammatory activity remained unexplored. In our study we have reported for the first time the anti-inflammatory activity of gintonin on RAW 264.7 cells. We found that gintonin potently suppresses the nitric oxide production without any cytotoxicity at given doses and also efficiently suppressed the levels of proinflammatory cytokines. Moreover, it mediaes its signal transduction via MAPK and NF-κB pathways and revives the levels of mir-34a and mir-93. These findings are valuable for the anti-inflammatory effects of this new compound with particular reference to microRNA involvement in the ginseng family.

A simple method for the preparation of crude gintonin from ginseng root, stem, and leaf

Ginseng has been used as a general tonic agent to invigorate the human body as an adaptogenic agent. In a previous report, we have shown that ginseng contains a novel glycolipoprotein called gintonin. The main function of gintonin is to transiently enhance intracellular free Ca²⁺ [Ca²⁺]_i levels in animal cells. The previous method for gintonin isolation included multiple steps using organic solvents. In the present report, we developed a simple method for the preparation of crude gintonin from ginseng root as well as stem and leaf, which produced a higher yield of gintonin than the previous one. The yield of gintonin was 0.20%, 0.29%, and 0.81% from ginseng root, stem, and leaf, respectively. The apparent molecular weight of gintonin isolated from stem and leaf through sodium dodecyl sulfate polyacrylamide gel electrophoresis was almost same as that from root but the compositions of amino acids, carbohydrates or lipids differed slightly between them. We also examined the effects of crude gintonin from ginseng root, stem, and leaf on endogenous Ca²⁺-activated Cl- channel (CaCC) activity of Xenopus oocytes through mobilization of [Ca²⁺]_i. We found that the order of potency for the activation of CaCC was ginseng root > stem > leaf. The ED₅₀ was 1.4±1.4, 4.5±5.9, and 3.9±1.1 μg/mL for root, stem and leaf, respectively. In the present study, we demonstrated for the first time that in addition to ginseng root, ginseng stem and leaf also contain gintonin. Gintonin can be prepared from a simple method with higher yield of gintonin from ginseng root, stem, and leaf. Finally, these results demonstrate the possibility that ginseng stem and leaf could also be utilized for ginstonin preparation after a simple procedure, rather than being discarded.

Agonist-activated Ca2+ influx and Ca2+ -dependent Cl- channels in Xenopus ovarian follicular cells: functional heterogeneity within the cell monolayer

Xenopus follicles are endowed with specific receptors for ATP, ACh, and AII, transmitters proposed as follicular modulators of gamete growth and maturation in several species. Here, we studied ion-current responses elicited by stimulation of these receptors and their activation mechanisms using the voltage-clamp technique. All agonists elicited Cl(-) currents that depended on coupling between oocyte and follicular cells and on an increase in intracellular Ca(2+) concentration ([Ca(2+) ](i)), but they differed in their activation mechanisms and in the localization of the molecules involved. Both ATP and ACh generated fast Cl(-) (F(Cl)) currents, while AII activated an oscillatory response; a robust Ca(2+) influx linked specifically to F(Cl) activation elicited an inward current (I(iw,Ca)) which was carried mainly by Cl(-) ions, through channels with a sequence of permeability of SCN(-)  > I(-)  > Br(-)  > Cl(-). Like F(Cl), I(iw,Ca) was not dependent on oocyte [Ca(2+) ](i) ; instead both were eliminated by preventing [Ca(2+) ](i) increase in the follicular cells, and also by U73122 and 2-APB, drugs that inhibit the phospolipase C (PLC) pathway. The results indicated that F(Cl) and I(iw,Ca) were produced by the expected, PLC-stimulated Ca(2+) -release and Ca(2+) -influx, respectively, and by the opening of I(Cl(Ca)) channels located in the follicular cells. Given their pharmacological characteristics and behavior in conditions of divalent cation deprivation, Ca(2+) -influx appeared to be driven through store-operated, calcium-like channels. The AII response, which is also known to require PLC activation, did not activate I(iw,Ca) and was strictly dependent on oocyte [Ca(2+) ](i) increase; thus, ATP and ACh receptors seem to be expressed in a population of follicular cells different from that expressing AII receptors, which were coupled to the oocyte through distinct gap-junction channels.

Effect of sertraline on [Ca2+](i) and viability of human MG63 osteosarcoma cells

The antidepressant, sertraline, has been shown to have diverse in vitro effects. This study examined whether sertraline altered [Ca(2+)](i) in MG63 human osteosarcoma cells by using fura-2 as a Ca(2+)-sensitive fluorescent dye. At 50-200 µM, sertraline induced a [Ca(2+)](i) rise in a concentration-dependent manner. Ca(2+) response was decreased by removing extracellular Ca(2+), suggesting that Ca(2+) entry and release contributed to the [Ca(2+)](i) signal. Sertraline-induced Ca(2+) entry was inhibited by nifedipine, La(3+), Gd(3+), and SK&F96365. When extracellular Ca(2+) was removed, pretreatment with the endoplasmic reticulum (ER) Ca(2+) pump inhibitor, thapsigargin, or 2,5-di-tert-butylhydroquinone (BHQ) abolished the sertraline-evoked [Ca(2+)](i) rise. Incubation with sertraline also abolished the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C (PLC) with U73122 abolished the sertraline-induced [Ca(2+)](i) rise. At 20-30 µM, overnight treatment with sertraline killed cells in a concentration-dependent manner. The cytotoxic effect of sertraline was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/propidium iodide staining data demonstrate that sertraline (30 µM) evoked apoptosis. Sertraline (20 and 30 µM) also increased levels of reactive oxygen species. Together, in human osteosarcoma cells, sertraline evoked a [Ca(2+)](i) rise by inducing PLC-dependent Ca(2+) release from the ER and Ca(2+) entry by L-type Ca(2+) channels and store-operated Ca(2+) channels. Sertraline induced cell death that may involve apoptosis by mitochondrial pathways.

Inhibitory effects of dextrorotatory morphinans on the human 5-HT(3A) receptor expressed in Xenopus oocytes: Involvement of the N-terminal domain of the 5-HT(3A) receptor

We previously developed a series of dextromethorphan (DM, 3-methoxy-17-methylmorphinan) analogs modified at positions 3 and 17 of the morphinan ring system. Recent reports have shown that DM attenuates abdominal pain caused by irritable bowel syndrome, and multidrug regimens that include DM prevent nausea/vomiting following cancer surgery. However, little is known regarding the molecular mechanisms underlying the beneficial effects of DM. Here, we investigated the effects of DM, 3 of its analogs (AM, 3-allyloxy-17-methoxymorphian; CM, 3-cyclopropyl-17-methoxymorphinan; and DF, 3-methyl-17-methylmorphinan), and 1 of its metabolites (HM, 3-methoxymorphinan) on the activity of the human 5-HT(3A) receptor channel expressed in Xenopus laevis oocytes, using the 2-microelectrode voltage clamp technique. We found that intra-oocyte injection of human 5-HT(3A) receptor cRNAs elicited an inward current (I(5-HT)) in the presence of 5-HT. Cotreatment with AM, CM, DF, DM, or HM inhibited I(5-HT) in a dose-dependent, voltage-independent, and reversible manner. The IC(50) values for AM, CM, DF, DM, and HM were 24.5±1.4, 21.5±4.2, 132.6±35.8, 181.3±23.5, and 191.3±31.5μM, respectively. The IC(50) values of AM and CM were 7-fold lower than that of DM, and mechanistic analysis revealed that DM, DF, HM, AM, and CM were competitive inhibitors of I(5-HT). Point mutations of Arg241 in the N-terminal, but not amino acids in the pore region, to other amino acid residues attenuated or abolished DM- and DM-analog-induced inhibition of I(5-HT). Together, these results demonstrated that dextrorotatory morphinans might regulate 5-HT(3A) receptor channel activity via interaction with its N-terminal domain.

Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels in cultured rat hippocampal neurons

AIM

To investigate the effect of ginsenoside Rb1 on voltage-gated calcium currents in cultured rat hippocampal neurons and the modulatory mechanism.

METHODS

Cultured hippocampal neurons were prepared from Sprague Dawley rat embryos. Whole-cell configuration of the patch-clamp technique was used to record the voltage-gated calcium currents (VGCCs) from the hippocampal neurons,and the effect of Rb1 was examined.

RESULTS

Rb1 (2-100 μmol/L) inhibited VGCCs in a concentration-dependent manner, and the current was mostly recovered upon wash-out. The specific L-type Ca(2+) channel inhibitor nifedipine (10 μmol/L) occluded Rb1-induced inhibition on VGCCs. Neither the selective N-type Ca(2+) channel blocker ω-conotoxin-GVIA (1 μmol/L), nor the selective P/Q-type Ca(2+) channel blocker ω-agatoxin IVA (30 nmol/L) diminished Rb1-sensitive VGCCs. Rb1 induced a leftward shift of the steady-state inactivation curve of I(Ca) to a negative potential without affecting its activation kinetics or reversal potential in the I-V curve. The inhibitory effect of Rb1 was neither abolished by the adenylyl cyclase activator forskolin (10 μmol/L), nor by the PKA inhibitor H-89 (10 μmol/L).

CONCLUSION

Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels, without affecting the N-type or P/Q-type Ca(2+) channels in hippocampal neurons. cAMP-PKA signaling pathway is not involved in this effect.

Effects of ginsenoside on pacemaker potentials of cultured interstitial cells of Cajal clusters from the small intestine of mice

Ginsenoside, one of the active ingredients of Panax ginseng, has a variety of physiological and pharmacological actions in various organs. However, little is known about the effects of ginsenosides on gastrointestinal (GI) motility. We studied the modulation of pacemaker potentials by ginsenoside in the interstitial cells of Cajal (ICCs) using the whole-cell patch clamp technique in the current clamp mode. Among ginsenosides, we investigated the effects of ginsenoside Rb1, Rg3 and Rf. While externally applied Rb1 and Rg3 had no effects on pacemaker potentials, Rf caused membrane depolarization. The application of flufenamic acid or niflumic acid abolished the generation of pacemaker potentials and inhibited the Rf-induced membrane depolarization. Membrane depolarization induced by Rf was not inhibited by intracellular application of guanosine 5'-[β-thio]diphosphate trilithium salt. Pretreatment with a Ca(2+)-free solution, thapsigargin, a Ca(2+)-ATPase inhibitor of the endoplasmic reticulum, U-73122, a phospholipase C inhibitor, or 2-APB, an IP3 receptor inhibitor, abolished the generation of pacemaker potentials and suppressed Rfinduced actions. However, treatment with chelerythrine and calphostin C, protein kinase C inhibitors, did not block Rf-induced effects on pacemaker potentials. These results suggest that ginsenoside Rf modulates the pacemaker activities of ICCs and thereby regulates intestinal motility.

Protection against kainate neurotoxicity by ginsenosides: attenuation of convulsive behavior, mitochondrial dysfunction, and oxidative stress

We previously demonstrated that kainic acid (KA)-mediated mitochondrial oxidative stress contributed to hippocampal degeneration and that ginsenosides attenuated KA-induced neurotoxicity and neuronal degeneration. Here, we examined whether ginsenosides affected KA-induced mitochondrial dysfunction and oxidative stress in the rat hippocampus. Treatment with ginsenosides attenuated KA-induced convulsive behavior dose-dependently. KA treatment increased lipid peroxidation and protein oxidation and decreased the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio to a greater degree in the mitochondrial fraction than in the hippocampal homogenate. KA treatment resulted in decreased Mn-superoxide dismutase expression and diminished the mitochondrial membrane potential. Furthermore, KA treatment increased intramitochondrial Ca(2+) and promoted ultrastructural degeneration in hippocampal mitochondria. Treatment with ginsenosides dose-dependently attenuated convulsive behavior and the KA-induced mitochondrial effects. Protection appeared to be more evident in mitochondria than in tissue homogenates. Collectively, the results suggest that ginsenosides prevent KA-induced neurotoxicity by attenuating mitochondrial oxidative stress and mitochondrial dysfunction.

Effects of ginseng saponin on acute cocaine-induced alterations in evoked dopamine release and uptake in rat brain nucleus accumbens

In traditional medicine, Panax ginseng has been used to treat various behavioral effects of psychostimulants (e.g., cocaine) and other drugs of abuse and to ameliorate withdrawal symptoms. The neurochemical bases for this efficacy, however, remain to be elucidated. We previously used the real-time fast-scan cyclic voltammetry in rat nucleus accumbens slices to demonstrate that cocaine not only enhances DA release evoked by single-pulse electrical stimulation and inhibits DA uptake during application but also further increases the release upon washout (termed a "rebound" release enhancement). In the present study, we determined whether co-application and washout of ginseng total saponin (GTS), the active ingredient of Panax ginseng, with cocaine attenuate cocaine-induced enhancement of evoked DA release, DA uptake inhibition and/or withdrawal-associated rebound enhancement. Cocaine rapidly potentiated the DA release within the first 10 min of application, and acute cocaine withdrawal caused a rebound increase. Co-application of GTS with cocaine inhibited the release enhancement and subsequently prevented the rebound increase during acute withdrawal. The effect of GTS was concentration-dependent. In contrast, GTS had no significant effects on the cocaine-mediated DA uptake inhibition. These results suggest that the attenuation of the cocaine-induced enhancement of impulse-dependent DA release, rather than uptake inhibition, might be one of the pharmacological bases for attenuation of behavioral effects of cocaine and amelioration of acute withdrawal symptoms by ginseng.

Panax ginseng induces anterograde transport of pigment organelles in Xenopus melanophores

Melanophores from Xenopus laevis are pigmented cells, capable of quick colour changes through cyclic adenosine 3':5'-monophosphate (cAMP) coordinated transport of their intracellular pigment granules, melanosomes. In this study we use the melanophore cell line to evaluate the effects of Panax ginseng extract G115 on organelle transport. Absorbance readings of melanophore-coated microplates, Correlate-EIA direct cAMP enzyme immunoassay kit, and western blot were used to measure the melanosome movement and changes in intracellular signalling. We show that Panax ginseng induces a fast concentration-dependent anterograde transport of the melanosomes. No significant increase in the cAMP level was seen and pre-incubation of melanophores with the protein kinase C (PKC) inhibitor EGF-R Fragment 651-658 (M-EGF) only partly decreased the ginseng-induced dispersion. We also demonstrate that Panax ginseng, endothelin-3 (ET-3) and alpha-melanocyte stimulating hormone (MSH) stimulate an activation of mitogen activated protein kinase (MAPK). Pre-incubation with M-EGF decreased the MAPK activity induced by ET-3 and MSH, but again only marginally affected the response of Panax ginseng. Thus, in melanophores we suggest that Panax ginseng stimulates an anterograde transport of pigment organelles via a non-cAMP and mainly PKC-independent pathway.

Effects of ginseng total saponins on pacemaker currents of interstitial cells of Cajal from the small intestine of mice

Although ginsenosides have a variety of physiologic or pharmacologic functions in various regions, there are only a few reports on the effects of ginsenosides on gastrointestinal (GI) motility. We studied the modulation of pacemaker activities by ginseng total saponins in the interstitial cells of Cajal (ICC) using the whole cell patch-clamp technique. Externally applied ginseng total saponins (GTS) produced membrane depolarization in the current-clamp mode and increased tonic inward pacemaker currents in the voltage-clamp mode. The application of flufenamic acid or niflumic acid abolished the generation of pacemaker currents, but only treatment with flufenamic acid inhibited the GTS-induced tonic inward currents. The tonic inward currents induced by GTS were not inhibited by the intracellular application of guanosine 5'-[beta-thio]diphosphate trilithium salt. Pretreatment with a Ca(2+)-free solution, with U-73122, an active phospholipase C inhibitor, and with thapsigargin, a Ca(2')-ATPase inhibitor of the endoplasmic reticulum, abolished the generation of pacemaker currents and suppressed the GTS-induced action. However, treatment with chelerythrine and calphostin C, protein kinase C inhibitors, did not block the GTS-induced effects on the pacemaker currents. These results suggest that ginsenosides modulate the pacemaker activities of the ICC, and the ICC can be targets for ginsenosides, and their interaction can affect intestinal motility.

Neuroprotective effect of individual ginsenosides on astrocytes primary culture

Most of the known pharmacological effects of Panax ginseng on the central nervous system are due to its major components - ginsenosides. Although the antioxidant ability of ginseng root has already been established, this activity has never been evaluated for isolated ginsenosides on astrocytes. The activity of protopanaxadiols Rb(1), Rb(2), Rc and Rd, and protopanaxatriols Re and Rg(1) was evaluated in vitro on astrocytes primary culture by means of an oxidative stress model with H(2)O(2). The viability of astrocytes was determined by the MTT reduction assay and by the LDH release into the incubation medium. The effects on the antioxidant enzymes catalase, superoxide dismutase (SOD), glutathione peroxidases (GPx) and glutathione reductase (GR) and on the intracellular reactive oxygen species (ROS) formation were also investigated. Exposure of astrocytes to H(2)O(2) decreased cell viability as well as the antioxidant enzymes activity and increased ROS formation. Oxidative stress produced significant cell death that was reduced by previous treatment with the tested ginsenosides. Ginsenosides Rb(1), Rb(2), Re and Rg(1) were effective in reducing astrocytic death, while Rb(1), Rb(2), Rd, Re and Rg(1) decreased ROS formation, ginsenoside Re being the most active. Ginsenosides from P. ginseng induce neuroprotection mainly through activation of antioxidant enzymes.

Protective effects of ginseng saponins on 3-nitropropionic acid-induced striatal degeneration in rats

The precise cause of neuronal cell death in Huntington's disease (HD) is not known. Systemic administration of 3-nitropropionic acid (3-NP), an irreversible succinate dehydrogenase inhibitor, not only induces a cellular ATP depletions but also causes a selective striatal degeneration similar to that seen in HD. Recent accumulating reports have shown that ginseng saponins (GTS), the major active ingredients of Panax ginseng, have protective effects against neurotoxin insults. In the present study, we examined in vitro and in vivo effects of GTS on striatal neurotoxicity induced by repeated treatment of 3-NP in rats. Here, we report that systemic administration of GTS produced significant protections against systemic 3-NP- and intrastriatal malonate-induced lesions in rat striatum with dose-dependent manner. GTS also improved significantly 3-NP-caused behavioral impairment and extended survival. However, GTS itself had no effect on 3-NP-induced inhibition of succinate dehydrogenase activity. To explain the mechanisms underlying in vivo protective effects of GTS against 3-NP-induced striatal degeneration, we examined in vitro effect of GTS against 3-NP-caused cytotoxicity using cultured rat striatal neurons. We found that GTS inhibited 3-NP-induced intracellular Ca(2+) elevations. GTS restored 3-NP-caused mitochondrial transmembrane potential reduction in cultured rat striatal neurons. GTS also prevented 3-NP-induced striatal neuronal cell deaths with dose-dependent manner. The EC(50) was 12.6 +/- 0. 7microg/ml. These results suggest that in vivo protective effects of GTS against 3-NP-induced rat striatal degeneration might be achieved via in vitro inhibition of 3-NP-induced intracellular Ca(2+) elevations and cytotoxicity of striatal neurons.

Effect of calmodulin on ginseng saponin-induced Ca2+-Activated CI-channel activation inXenopus laevis oocytes

We previously demonstrated the ability of ginseng saponins (active ingredients of Panax ginseng) to enhance Ca2+-activated Cl- current. The mechanism for this ginseng saponin-induced enhancement was proposed to be the release of Ca2+ from IP3-sensitive intracellular stores through the activation of PTX-insensitive Galpha(q/11) proteins and PLC pathway. Recent studies have shown that calmodulin (CaM) regulates IP3 receptor-mediated Ca2+ release in both Ca2+-dependent and -independent manner. In the present study, we have investigated the effects of CaM on ginseng saponin-induced Ca2+-activated Cl- current responses in Xenopus oocytes. Intraoocyte injection of CaM inhibited ginseng saponin-induced Ca2+-activated Cl- current enhancement, whereas co-injection of calmidazolium, a CaM antagonist, with CaM blocked CaM action. The inhibitory effect of CaM on ginseng saponin-induced Ca2+-activated Cl- current enhancement was dose- and time-dependent, with an IC50 of 14.9 +/- 3.5 microM. The inhibitory effect of CaM on saponin's activity was maximal after 6 h of intraoocyte injection of CaM, and after 48 h the activity of saponin recovered to control level. The half-recovery time was calculated to be 16.7 +/- 4.3 h. Intraoocyte injection of CaM inhibited Ca2+-induced Ca2+-activated Cl- current enhancement and also attenuated IP3-induced Ca2+-activated Cl- current enhancement. Ca2+/CaM kinase II inhibitor did not inhibit CaM-caused attenuation of ginseng saponin-induced Ca2+-activated Cl- current enhancement. These results suggest that CaM regulates ginseng saponin effect on Ca2+-activated Cl current enhancement via Ca2+-independent manner.