Biomedical subjects

Q Y Liu

Publications and source records attributed to Q Y Liu.

At least 55 records · Page 3Linked to original sources

PubMed1997

GABA induces GABAergic MSCs in cultured embryonic rat thalamic neurons.

Application of 0.1-10 microM GABA in the vicinity of cultured embryonic rat thalamic neurons recorded with patch pipettes in the presence of 2 microM TTX induced or increased the frequency of miniature synaptic currents (MSCs) that reversed polarity at the Cl- equilibrium potential. These MSCs were blocked by the GABAA receptor antagonist bicuculline and exhibited exponential decay kinetics that closely paralleled those estimated from fluctuation analysis of Cl- channels activated pharmacologically by applying 1-10 microM GABA to the same cells. We conclude that the MSCs are mediated by GABA. Application of the GABAA receptor agonist muscimol activated Cl- current but failed to induce GABAergic MSCs while submicromolar concentrations of GABA evoked GABAergic MSCs but did not activate Cl- channels. The GABAB receptor agonist (-)baclofen did not mimic GABA in inducing MSCs. Induction of GABAergic MSCs by GABA required extracellular Ca2+. Verapamil and Co2+, which block voltage-dependent calcium channels, completely blocked GABA-induced MSCs independent of their effects on the direct activation of a Cl- current response. The results indicate that GABA can trigger GABAergic Cl(-)-dependent MSCs in a Cao(2+)-dependent manner. The mechanism may involve a novel receptor and/or signal transduction pathway.

Animals↗

PubMed1997

DNase I primary transcript is alternatively spliced in both normal and apoptotic cells: no evidence of up-regulation in apoptosis.

The reverse transcriptase polymerase chain reaction (RT-PCR) was used to elucidate the expression of DNase I and its possible involvement in apoptotic genome degradation. Multiple PCR products were obtained from cDNAs of different rat and human cells. The subsequent cloning and sequence analysis of seven PCR products revealed that only one of them had the expected size (639 bp) and sequence identity to that of rat DNase I cDNA. The other six PCR products were characterized by either sequence insertions or deletions. To establish the origin of this molecular diversity, a genomic fragment of the rat DNase I gene was also isolated, subcloned, and sequenced. Sequence comparison of six cDNAs with the rat genomic DNA revealed that they, indeed, resulted from inclusion of introns or deletion of exons. Southern hybridizations of the RT-PCR products from a variety of mammalian cell lines, using the major DNase I cDNA fragment as a probe, showed that in some cells as many as 20 alternatively spliced transcripts could be detected. This complexity of splice variants was widespread, and cell-specific profiles differed by the relative concentration of each transcript. None of these spliced transcripts maintained an open reading frame containing an intact catalytic site, suggesting that they do not encode any functional proteins. These complicated alternative splicing events might, however, significantly contribute to the regulation of DNase I expression. There was no apparent increase of the major DNase I transcript after induction of apoptosis in the cell lines studied. Apoptotic cells appeared to have similar normal/alternative transcript ratios as the control cells, suggesting that DNase I may not be the endonuclease involved in DNA degradation during apoptosis.

3T3 Cells↗

PubMed1997

Imipramine blocks the transient outward potassium current in rat ventricular myocytes.

AIM: To examine the effects of imipramine on transient outward potassium current (I(to) in rat ventricular myocytes. METHODS: The patch-clamp whole-cell recording techniques were used. RESULTS: Imipramine resulted in a concentration-dependent inhibition of I(to) with the IC50 of 6.0 mumol.L-1 and a concentration-dependent acceleration of I(to) inactivation. The blocking showed no difference at different testing membrane potentials. Imipramine produced slight effects (about 3 and 4 mV, respectively) on steady-state activation and inactivation curves of I(to), and tended to prolong the recovery of I(to) from inactivation (tau control = 37 +/- 11 ms; tau drug = 58 +/- 17 ms), but not significant (n = 4, P > 0.05). The inhibitory effect of imipramine on Ito was increased when the prepulses were prolonged progressively from 0 to 120 ms. (tau control = 22 +/- 8 ms; tau drug = 14 +/- 5 ms). CONCLUSIONS: Imipramine blocked Ito in concentration-dependent but voltage-independent manners, and with "open channel blocking" properties.

Animals↗

PubMed1997

[The blocking effects of six antiarrhythmic drugs on transient outward current in rat ventricular myocytes].

The effects of six antiarrhythmic drugs on transient outward current (Ito) in rat ventricular myocytes were examined by using the patch-clamp whole-cell recording technique. Quinidine, nifedipine, and imipramine resulted in a concentration-dependent inhibition of Ito with IC50s of 5.4, 10.9 and 6.0 mumol.L-1, respectively. All three agents produced a concentration-dependent increase in the rate of inactivation of Ito. Disopyramide, procainamide and E-4031 produced little inhibition of Ito even when present at 100 mumol.L-1. The results from this study show that quinidine, nifedipine and imipramine are potent inhibitors of Ito and that inhibition is mediated through preferential interaction with the open channel.

Animals↗

PubMed1997

Alpha 1D L-type Ca(2+)-channel currents: inhibition by a beta-adrenergic agonist and pituitary adenylate cyclase-activating polypeptide (PACAP) in rat pinealocytes.

In this study the subunits of the dihydropyridine-sensitive L-type Ca2+ channels (L-channels) expressed in rat pinealocytes were characterized using reverse transcription (RT)-PCR analysis, and the modulation of these channels by adrenergic agonists and by pituitary adenylate cyclase-activating polypeptide (PACAP) was studied using the patch-clamp technique. RT-PCR analysis showed that rat pinealocytes expressed alpha 1D, alpha 2b, beta 2, and beta 4 Ca(2+)-channel subunit mRNAs. Other alpha 1 subunit transcripts were either not expressed or present at very low levels, indicating that the pinealocytes express predominantly alpha 1D L-channels. Electrophysiological studies confirmed that the pineal expressed a single population of L-channels. The L-channel currents were inhibited by two agonists that elevate cyclic AMP: the beta-adrenergic agonist isoproterenol and PACAP. Similar inhibition was observed with a cyclic AMP analogue, 8-bromo-cyclic AMP. The presence of a cyclic AMP antagonist, Rp-adenosine 3',5'-cyclic monophosphorothioate, blocked the inhibition by isoproterenol and PACAP. Norepinephrine, a mixed alpha- and beta-adrenergic agonist, also inhibited the L-channel currents, but the inhibition was smaller. The smaller inhibition by norepinephrine was secondary to the simultaneous activation of alpha- and beta-adrenergic receptors. These results indicate that (a) pinealocytes express predominantly alpha 1D L-channels, and (b) the beta-adrenergic agonist isoproterenol and PACAP inhibit the L-channel currents through elevation of cyclic AMP. However, an alpha-adrenergic-mediated mechanism also appears to be involved in the effect of norepinephrine on the L-channel currents.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1997

Taxol and estramustine-induced modulation of human prostate cancer cell apoptosis via alteration in bcl-xL and bak expression.

bcl-xL is an antiapoptotic protein that shares sequence homology with bcl-2 and seems to convey chemoresistance in many human tumor cell lines. bcl-xL protein is expressed at a 3-fold higher level in PC-3 cells than it is in LNCaP cells. Taxol causes apoptosis in both these cell lines, as measured by the formation of DNA ladders and by the observation of typical cellular morphological changes (chromatin condensation and nuclear fragmentation) after 4', 6-diamidino-2-phenylindole staining. Overexpression of bcl-2 in LNCaP cells did not prevent Taxol-induced apoptosis. Treatment of LNCaP cells with 10 nm Taxol led, after 24 h, to relatively specific and almost total down-regulation of bcl-xL protein in the absence of alteration of bax, bak, or bcl-2 levels. This change was paralleled by a similar decrease in the level of bcl-xL mRNA, as demonstrated by reverse transcription-PCR. The level of glyceraldehyde-3-phosphate dehydrogenase mRNA was not changed. In PC-3 cells, 48 h were required for both maximal bcl-xL protein down-regulation and cellular apoptosis. In contrast, treatment of LNCaP cells with estramustine induced apoptosis, but this was not associated with any change in the intracellular level of bcl-xL or bax protein. Instead, relatively specific 2-fold up-regulation of the proapoptotic protein bak was observed. In PC-3 cells, cellular apoptosis induced by estramustine was bak independent. These results augment our understanding of the importance of bcl-xL in prostate cancer and suggest that appropriate manipulation of cytotoxic chemotherapeutic agents may favorably alter the balance between pro- and antiapoptotic proteins in this tumor.

Apoptosis↗

PubMed1996

Activation and inhibition of reconstituted cardiac L-type calcium channels by palmitoyl-L-carnitine.

We have studied the effect of a palmitoyl-L-carnitine (L-PC) on single cardiac L-type Ca channels incorporated from porcine ventricular sarcolemma into planar lipid bilayers where we could control the concentration, intracellular and/or extracellular location, and duration of L-PC treatment. We found that 1.0 microM L-PC in either the intracellular or extracellular chamber caused an approximately 8 fold increase in channel open probability when measured within the first minute after L-PC addition. Higher concentrations of L-PC did not increase open probability to the same extent as 1.0 microM. In addition, we found that L-PC had biphasic effects on the open probability of L-type Ca channels, causing an increase in activity immediately after the addition of L-PC, but leading to a decrease in open probability after a few minutes. Higher concentrations of L-PC (10 microM) also caused a decrease in single-channel conductance from 26 to 21 pS (measured in 100 mM external Ba2+). The effects of L-PC were similar on both sides of the channels, suggesting that alterations in the physical properties of the membrane surrounding the channels may be responsible for the effects of L-PC. These changes in Ca channel activity may participate in the generation of abnormal electrical activity and arrhythmogenesis during ischemia.

Animals↗

PubMed1996

Upregulation of GABAA current by astrocytes in cultured embryonic rat hippocampal neurons.

Embryonic rat hippocampal neurons were cultured on poly-D-lysine (PDL) or a monolayer of postnatal cortical astrocytes to reveal putative changes in neuronal physiology that involve astrocyte-derived signals during the first 4 d of culture, GABA-induced Cl- current (IGABA) was quantified using outside-out and whole-cell patch-clamp recordings beginning at 30 min, when cells had become adherent. The amplitude and density (current normalized to membrane capacitance) of IGABA in neurons grown on astrocytes became statistically greater than that recorded in neurons grown on PDL after 2 hr in culture (HIC). Although the current density remained unchanged in neurons on astrocytes, that in neurons on PDL decreased and became statistically lower beginning after 2 HIC. The differences in amplitude and density of IGABA in the two groups of neurons were maintained during the 4 d experiment. The upregulation effect of astrocytes on neuronal IGABA required intimate contact between the neuronal cell body and underlying astrocytes. Suppression of spontaneous Cac2+ elevations in astrocytes by bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid that was loaded intracellularly decreased their modulatory effects on IGABA. IGABA in all cells was blocked completely by bicuculline and exhibited virtually identical affinity constants, Hill coefficients, and potentiation by diazepam in the two groups. Outside-out patch recordings revealed identical unitary properties of IGABA in the two groups. More channels per unit of membrane area could explain the astrocyte enhancement of IGABA. The results reveal that cortical astrocytes potentiate IGABA in hippocampal neurons in a contact-dependent manner via a mechanism involving astrocyte Cac2+ elevation.

Animals↗

PubMed1996

Inhibitory effects of activin on the growth and morpholgenesis of primary and transformed mammary epithelial cells.

Activin is a member of the transforming growth factor beta superfamily, which is known to have activities involved in regulating differentiation and development. By using reverse transcription-PCR analysis on immunoaffinity-purified human breast cells, we have found that activin beta a and activin type II receptor are expressed by myoepithelial cells, whereas no expression was detected in other breast cell types. In examining 15 breast cell lines, we have found only four (HBL-100, MCF10-A, PMC-42, and BT 20) to be positive for activin beta a mRNA, whereas all expressed the activin type II receptor. Furthermore, we have found activin A to be a potent growth inhibitor of MCF- 7 cells (at 2 ng/ml), where it causes an arrest in G(1). Activin A does not appear to have an effect on the cell cycle of primary myoepithelial or luminal cells. However, we demonstrate that activin is an inhibitor of tubule formation by human mammary organoids in vitro. These are the first observations of activin and activin receptor in the normal human breast and in human breast cell lines and suggest a role for activin in mammary cell growth and morphogenesis.

Activins↗

PubMed1996

Elongation factor 1 alpha genes of the red alga Porphyra purpurea include a novel, developmentally specialized variant.

The life cycle of the red alga Porphyra purpurea alternates between two morphologically distinct phases: a shell-boring, filamentous sporophyte and a free-living, foliose gametophyte. From a subtracted cDNA library enriched for sporophyte-specific sequences, we isolated a cDNA encoding an unusual elongation factor 1 alpha (EF-1 alpha) that is expressed only in the sporophyte. A second EF-1 alpha gene that is expressed equally in the sporophyte and the gametophyte was isolated from a genomic library. These are the only EF-1 alpha genes detectable in P. purpurea. The constitutively expressed gene encodes an EF-1 alpha very similar to those of most eukaryotes. However, the sporophyte-specific EF-1 alpha is one of the most divergent yet described, with nine insertions or deletions ranging in size from 1 to 26 amino acids. This is the first report of a developmental stage-specific EF-1 alpha outside of the animal kingdom and suggests a fundamental role for EF-1 alpha in the developmental process.

Amino Acid Sequence↗

PubMed1996

Expression and characterization of a novel human sperm membrane protein.

A cDNA fragment (HSD-1) coding for part of a human sperm membrane protein (hSMP-1) was previously isolated from a human testis cDNA expression library, with the serum from an infertile patient used as a probe. By rescreening human testis cDNA libraries with the HSD-1 insert and using rapid amplification of cDNA ends, the complete cDNA of 2482 bp was identified and sequenced. An open reading frame of 1572 bp encodes 523 amino acid residues with a computed molecular mass of 55.08 kDa. This protein sequence does not match any other sequence in the databases, indicating that it represents a novel sperm antigen. Northern blot analysis of human and rat testis poly(A) mRNA detected a band of approximately 2.5 kb in both species. Reverse transcriptase polymerase chain reaction analysis showed that hSMP-1 mRNA was present in human testis but was not in either kidney or liver. When the cDNA was expressed in Escherichia coli under the control of the T7 promoter, the expressed protein accumulated to a level of about 50% of the total cellular protein. The expressed protein, which contained an N-terminal poly(his) sequence tag, was purified by chromatography on an nitrilo-tri-acetic acid affinity resin. Approximately 10 mg of pure protein was obtained from a 500-ml culture, purified, and used as antigen to generate a polyclonal antiserum in rabbits. Western blot analysis of human sperm extracts showed a single specific band at 55.5 kDa. Immunofluorescence data showed that hSMP-1 was localized to the head of human sperm. The fluorescent staining formed a cap-shaped pattern that was similar in morphology to the human sperm acrosome. The availability of large amounts of recombinant hSMP-1 and its antiserum will facilitate studies on the function and expression of the protein during spermatogenesis and the assessment of its potential value as a contraceptive immunogen.

Amino Acid Sequence↗

PubMed1996

Organizational characteristics and information content of an archaeal genome: 156 kb of sequence from Sulfolobus solfataricus P2.

We have initiated a project to sequence the 3 Mbp genome of the thermoacidophilic archaebacterium Sulfolobus solfataricus P2. Cosmids were selected from a provisional set of minimally overlapping clones, subcloned in pUC18, and sequenced using a hybrid (random plus directed) strategy to give two blocks of contiguous unique sequence, respectively, 100,389 and 56,105 bp. These two contigs contain a total of 163 open reading frames (ORFs) in 26-29 putative operons; 56 ORFs could be identified with reasonable certainty. Clusters of ORFs potentially encode proteins of glycogen biosynthesis, oxidative decarboxylation of pyruvate, ATP-dependent transport across membranes, isoprenoid biosynthesis, protein synthesis, and ribosomes. Putative promoters occur upstream of most ORFs. Thirty per cent of the predicted strong and medium-strength promoters can initiate transcription at the start codon or within 10 nucleotides upstream, indicating a process of initial mRNA-ribosome contact unlike that of most eubacterial genes. A novel termination motif is proposed to account for 15 additional terminations. The two contigs differ in densities of ORFs, insertion elements and repeated sequences; together they contain two copies of the previously reported insertion sequence ISC 1217, five additional IS elements representing four novel types, four classes of long non-IS repeated sequences, and numerous short, perfect repeats.

Chromosomes, Bacterial↗

PubMed1996

On the antiarrhythmic actions of magnesium in single guinea-pig ventricular myocytes.

1. The hypotheses that magnesium quickly abolishes arrhythmias by acting as a calcium antagonist or by increasing outward potassium currents were tested in guinea-pig isolated ventricular myocytes by recording membrane potentials and currents by means of a single microelectrode discontinuous voltage clamp method. 2. High [Mg2+]o (4-16 mmol/L) slightly increased the amplitude and duration of the action potential (AP) in some myocytes, but overall the changes were not significant. 3. High [Mg2+]o did not decrease the slow inward current (ICa) and had little effect on voltage- and time-dependent outward potassium currents whether or not ICa was allowed to flow. 4. Zero [Mg2+]o decreased the duration, but not amplitude, of the AP. Zero [Mg2+]o had little effect on ICa and on outward currents except for a small increase in outward current in the region of the negative slope of the inward rectifier current-voltage relationship. 5. In our myocytes, in contrast to [Mg2+]o, high [Ca2+]o significantly increased the amplitude and decreased the duration of the AP; at the same time, high [Ca2+]o increases ICa and the outward potassium current. 6. High [Mg2+]o decreased the amplitude of the oscillatory potentials (Vos)induced by various Ca(2+)-overloading procedures (high [Ca2+]o, noradrenaline, strophanthidin and barium). 7. It is concluded that the mechanisms by which high [Mg2+]o quickly suppresses cardiac arrhythmias are related to an extracellular action of Mg2+ and do not include a block of ICa or an increase in outward current. Mg2+ can be antiarrhythmic by decreasing Vos amplitude and possibly by screening the fixed negative charges at the external surface of the sarcolemma.

Action Potentials↗

PubMed1996

Age-related differences in beta-adrenergic regulation of repolarization in canine epicardial myocytes.

Developmental changes occur in beta-adrenergic modulation of repolarization in canine. Purkinje fibers that may have important implications for rhythm and arrhythmias. No comparable data exist for ventricular myocardium. Therefore, we studied developmental changes in beta-adrenergic regulation of repolarization and delayed rectifier potassium current (IK) in canine ventricular epicardium. We first investigated the effects of isoproterenol (Iso) on action potentials (AP) recorded from epicardial slices with standard microelectrodes, and then we further determined the mechanisms of Iso action using the nystatin-perforated patch technique on isolated epicardial myocytes. In microelectrode studies Iso (10(-7) M) induced a shortening of the AP in preparations from adult dogs but not in those from dogs < 30 days old. These results were confirmed on AP recorded from single myocytes. Although the plateau was increased by Iso at all ages, the AP at 90% of repolarization was shortened (P < 0.05, n = 6) in adult but unchanged in < 30-day-old myocytes (NS, n = 6). Voltage-clamp studies showed that IK of adult cells was increased from a control value of 10.23 +/- 1.87 to 13.43 +/- 1.92 pA/pF with Iso (step to +50 mV, P < 0.05, n = 6), but IK was not modified in cells from young animals (6.49 +/- 2.72 pA/pF in control and 6.56 +/- 2.62 pA/pF with Iso, n = 4). Increasing the Iso concentration to 10(-5) M failed to increase IK significantly (n = 4). However, 10(-7) M Iso did increase L-type Ca2+ current from 172 +/- 31 to 262 +/- 42 pA (P < 0.05, n = 4), consistent with the effect to increase the AP plateau. These results show that there are developmental changes in beta-adrenergic regulation of repolarization in canine epicardium and that the control site of developmental changes is in the IK channel rather than the beta-adrenergic receptor cascade.

Action Potentials↗

PubMed1995

Isolation of pure populations of epithelial and myoepithelial cells from the normal human mammary gland using immunomagnetic separation with Dynabeads.

Monoclonal antibodies to epithelial membrane antigen and common acute lymphoblastic leukemia antigen were bound to second antibody-coated magnetic microspheres. These specific antibody/bead complexes were then used to directly isolate purified epithelial and myoepithelial cells from normal breast organoid cell preparations by magnetic separation. Near homogeneous cell populations were selected with yields of 10-20 x 10(6) epithelial and myoepithelial cells per organoid preparation. Repeated purification steps allowed almost complete depletion of myoepithelial cells for RNA studies. Tissue culture of separated cell populations in appropriate defined media further ensured purity of cell type and was unimpeded by Dynabead attachment.

Antibodies, Monoclonal↗

PubMed1995

Exogenous GABA persistently opens Cl- channels in cultured embryonic rat thalamic neurons.

We recorded whole-cell Cl- currents in cultured embryonic rat thalamic neurons by brief applications of GABA or the structural analogue muscimol. In 17 of 141 neurons (12%) the Cl- current persisted for a minute or more after the pipette was removed from the bath. Cl- current never persisted after muscimol exposure even in those cells exhibiting persistent GABA-activated currents (PGC). The half decay times (T50) of PGCs were exponentially and asymptotically related to the duration of GABA exposure and could be interrupted or completely aborted by low-pressure application of saline. PGCs were insensitive to membrane potential, to Tiagabine, a nipecotic acid analogue known to block GABA uptake, and persisted in Cao(2+)-free medium. Fluctuation analysis revealed that PGCs exhibited inferred Cl- channel properties whose kinetic components and estimated average elementary conductance showed no significant difference from those estimated during GABA exposure. The relative contribution of low frequency components was consistently reduced and that of high frequency components modestly increased during PGC compared to those recorded during GABA exposure. Taken together, the results suggest the existence of a superficial compartment in these embryonic neurons that can momentarily accumulate and release exogenous GABA.

Animals↗

PubMed1995

cGMP inhibits L-type Ca2+ channel currents through protein phosphorylation in rat pinealocytes.

In this study, the effect of cGMP on the dihydropyridine-sensitive (L-type) Ca2+ current was investigated using the whole cell version of the patch-clamp technique in rat pinealocytes. Dibutyryl-cGMP (1 x 10(-4) M) induced a pronounced inhibition of the L-type Ca2+ channel current. The dibutyryl-cGMP effect was concentration dependent. Elevation of cGMP by nitroprusside had a similar inhibitory action on the L-type Ca2+ channel current. Norepinephrine, which increased cGMP in rat pinealocytes, also inhibited this current. The action of cGMP was independent of cAMP elevation since the cAMP antagonist, Rp-cAMPs, had no effect on the inhibitory action of dibutyryl-cGMP. The involvement of cyclic GMP-dependent protein kinase was suggested by the blocking action of two protein kinase inhibitors, (1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) and N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA1004), on the dibutyryl-cGMP effect on the L-type Ca2+ channel current. Taken together, these results suggest that (1) cGMP modulates L-type Ca2+ channel currents in rat pinealocytes, causing inhibition of this current; (2) the action of cGMP appears to be independent of cAMP elevation; and (3) phosphorylation by cGMP-dependent protein kinase may be involved.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1995

Tetrandrine, a Ca++ antagonist: effects and mechanisms of action in vascular smooth muscle cells.

Tetrandrine, an alkaloid extracted from the Chinese medicinal herb Radix stephania tetrandrae, has traditionally been used to treat hypertension. In the present study, the effect of tetrandrine on vascular smooth muscle was investigated by using the rat tail artery as a model of a resistance vessel. Tetrandrine relaxes the tension in tail artery helical strips produced by depolarization with 60 mM KCl. Further studies show that tetrandrine inhibits the KCl-induced intracellular Ca++ increase and L-type voltage-dependent Ca++ channel currents, suggesting that tetrandrine relaxes the vessel via inhibition of Ca++ influx through Ca++ channels. Tetrandrine also inhibits norepinephrine (NE)-induced vasocontraction in the presence of extracellular Ca++. It does not, however, inhibit NE-induced vasocontraction in the absence of extracellular Ca++. Tetrandrine also inhibits the NE-induced intracellular Ca++ increase in the presence of extracellular Ca++ and has no effect on the NE-induced intracellular Ca++ increase in the absence of extracellular Ca++. This suggests that tetrandrine also blocks NE-induced Ca++ influx but not NE-induced Ca++ release from the intracellular Ca++ stores. Furthermore, tetrandrine inhibits thapsigargin-induced intracellular Ca++ concentration increase, suggesting that, in addition to blocking Ca++ influx, tetrandrine also may interfere with the interaction between thapsigargin and Ca++ adenosine triphosphatase.

Alkaloids↗