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PubMed2001

Function and expression of the epithelial Ca(2+) channel family: comparison of mammalian ECaC1 and 2.

1. The epithelial Ca(2+) channel (ECaC) family represents a unique group of Ca(2+)-selective channels that share limited homology to the ligand-gated capsaicin receptors, the osmolarity-sensitive channel OTRPC4, as well as the transient receptor potential family. Southern blot analysis demonstrated that this family is restricted to two members, ECaC1 and ECaC2 (also named CaT1). 2. RT-PCR analysis demonstrated that the two channels are co-expressed in calbindin-D-containing epithelia, including small intestine, pancreas and placenta, whereas kidney and brain only express ECaC1 and stomach solely ECaC2. 3. From an electrophysiological point of view, ECaC1 and ECaC2 are highly similar channels. Differences concern divalent cation permeability, the kinetics of Ca(2+)-dependent inactivation and recovery from inactivation. 4. Ruthenium red is a potent blocker of ECaC activity. Interestingly, ECaC2 has a 100-fold lower affinity for ruthenium red (IC(50) 9 +/- 1 microM) than ECaC1 (IC(50) 121 +/- 13 nM). 5. ECaCs are modulated by intracellular Mg(2+) and ATP. ECaC1 and ECaC2 activity rapidly decay in the absence of intracellular ATP. This effect is further accelerated at higher intracellular Mg(2+) concentrations. 6. In conclusion, ECaC1 and ECaC2 are homologous channels, with an almost identical pore region. They can be discriminated by their sensitivity for ruthenium red and show differences in Ca(2+)-dependent regulation.

Adenosine Triphosphate↗
PubMedDate not supplied

A comparison of the genes coding for canonical TRP channels and their M, V and P relatives.

The mammalian transient receptor potential (TRP) protein gene family consists of a diverse group of cation channels that currently contain at least 26 members. The physiologic functions of many remain unknown. They are structurally similar to Drosophila TRP and have a wide tissue distribution. In the present report, we compare the chromosomal locations, the gene, and primary structures of each of these 26 human TRP family members. Based on primary amino acid analyses, these channels comprise four different subfamilies: C- (canonical or classical), V- (or vanilloid receptor related), M- (melastatin related), and P (PKD)-type. The highest homology within each subfamily and between subfamilies exists in the predicted ion channel domains. Belonging to a given subfamily, however, does not determine the activating stimuli. This is exemplified by the V- and M-subfamilies, both of which have members that respond to temperature and osmolarity. TRP genes vary in their intron-exon organization, with the greatest diversity in the P subfamily. Chromosomal organization analyses revealed that two TRP members are found as direct repeats; TRPV3 follows TRPV1 and TRPV6 follows TRPV5. Both of these duplications appear to be recent as TRPV1 and V3 are more similar to each other than to other members of the TRPV subfamily. The same holds true for TRPV5 and V6. The article presents complication of comparisons including exon-intron boundaries, the amino acid sequence alignments, and the chromosomal organization of each of the presently known TRP channels.

Amino Acid Sequence↗
PubMed2005

Distinct expression of TRPM8, TRPA1, and TRPV1 mRNAs in rat primary afferent neurons with adelta/c-fibers and colocalization with trk receptors.

The transient receptor potential (TRP) superfamily of cation channels contains four temperature-sensitive channels, named TRPV1-4, that are activated by heat stimuli from warm to that in the noxious range. Recently, two other members of this superfamily, TRPA1 and TRPM8, have been cloned and characterized as possible candidates for cold transducers in primary afferent neurons. Using in situ hybridization histochemistry and immunohistochemistry, we characterized the precise distribution of TRPA1, TRPM8, and TRPV1 mRNAs in the rat dorsal root ganglion (DRG) and trigeminal ganglion (TG) neurons. In the DRG, TRPM8 mRNA was not expressed in the TRPV1-expressing neuronal population, whereas TRPA1 mRNA was only seen in some neurons in this population. Both A-fiber and C-fiber neurons expressed TRPM8, whereas TRPV1 was almost exclusively seen in C-fiber neurons. All TRPM8-expressing neurons also expressed TrkA, whereas the expression of TRPV1 and TRPA1 was independent of TrkA expression. None of these three TRP channels were coexpressed with TrkB or TrkC. The TRPM8-expressing neurons were more abundant in the TG compared with the DRG, especially in the mandibular nerve region innervating the tongue. Our data suggest heterogeneity of TRPM8 and TRPA1 expression by subpopulations of primary afferent neurons, which may result in the difference of cold-sensitive primary afferent neurons in sensitivity to chemicals such as menthol and capsaicin and nerve growth factor.

Animals↗
PubMed1998

Chromosomal localization and genomic characterization of the mouse melastatin gene (Mlsn1).

We recently described a novel gene, melastatin, whose expression is inversely correlated with melanoma aggressiveness. Chromosomal localization of this gene places it on mouse chromosome 7 and in the 15q13-q14 region of the human genome. Although expression patterns and chromosomal localization in the mouse are consistent with involvement of melastatin mutations in the mouse ruby-eye-2 defect, congenic analysis showed genetic segregation of the two loci. Cloning of the full-length human cDNA revealed a much larger transcript than we had previously identified, corresponding to a 1533-amino-acid protein product with homology to members of the transient receptor potential (Trp) family of calcium channels. The mouse melastatin gene contains 27 exons and spans at least 58 kb of genomic DNA. The promoter region of Mlsn1 contains four potential microphthalmia binding sites including an M box, a transcriptional regulatory element unique to genes with a restricted melanocytic expression pattern. A 1-kb PvuII fragment from this region was capable of driving high levels of luciferase expression in B16 melanoma cells.

Amino Acid Sequence↗
PubMed2005

Subcellular localization and trafficking of polycystins.

Polycystin-2 is a member of the transient receptor potential (TRP) family of ion channels that is mutated in autosomal dominant polycystic kidney disease. Although its function as a non-selective cation channel has been demonstrated in several model systems, the precise subcellular localization of polycystin-2 (TRPP2) in tubular epithelial cells has remained controversial. Recent evidence suggests that the subcellular localization of TRPP2 is regulated by multiple protein interactions. This review will summarize our current knowledge about polycystin trafficking and highlight the experimental data that supports a compartment-specific function of 'cystogenic' proteins.

Animals↗
PubMed2005

TRPM2 and TRPM7: channel/enzyme fusions to generate novel intracellular sensors.

Within the transient receptor potential (Trp) superfamily of ion channels, three members of the Trp (melastatin) (TRPM) subfamily stand out as their amino acid sequences indicate that they possess both ion channel and enzymatic functions. Recently, progress has been made in understanding the relationships between these disparate functionalities for two of these proteins, TRPM2 and TRPM7. TRPM2 appears to have adapted an ADP-ribose hydrolase (ADPRibase) enzyme's structure as a means of binding ADP-ribose and conveying information about the accumulation of ADP-ribose to the cell via the activation of Na(+)/Ca(2+) entry through the channel domain. While the ADPRibase activity of TRPM2's enzymatic domain is not required for channel gating, whether a converse relationship exists, wherein channel gating or ion flow modulates the enzymatic domain's ADPRibase activity, is not known. In contrast, TRPM7 appears to have evolved to place a Mg(2+)-regulated protein kinase domain in close proximity to a Mg(2+)-permeant ion channel, such that the kinase domain's phosphotransferase activity is able respond to local changes in free Mg(2+) occurring as the result of the flux of Mg(2+) through the channel. As with TRPM2, the activity of TRPM7's enzymatic domain is not required for gating of its channel domain, although evidence exists that it may have an alternative means of influencing channel gating. These insights into the functional relationships between the channel and enzymatic domains of TRPM2 and TRPM7 suggest informative models for their roles in vertebrate cell physiology.

Adenosine Diphosphate Ribose↗
PubMed2005

TRPM2: a calcium influx pathway regulated by oxidative stress and the novel second messenger ADP-ribose.

A unique functional property within the transient receptor potential (TRP) family of cation channels is the gating of TRP (melastatin) 2 (TRPM2) channels by ADP-ribose (ADPR). ADPR binds to the intracellular C-terminal tail of TRPM2, a domain that shows homology to enzymes with pyrophosphatase activity. Cytosolic Ca(2+) enhances TRPM2 gating by ADPR; ADPR and Ca(2+) in concert may be an important messenger system mediating Ca(2+) influx. Other stimuli of TRPM2 include NAD and H(2)O(2) and cyclic ADPR, which may act synergistically with ADPR. H(2)O(2), an experimental paradigm of oxidative stress, may also induce the formation of ADPR in the nucleus or mitochondria. In this review, we summarize the gating properties of TRPM2 and the proposed pathways of channel activation in vivo. TRPM2 is likely to be a key player in several signalling pathways, mediating cell death in response to oxidative stress or in reperfusion injury. Moreover, it plays a decisive role in experimentally induced diabetes mellitus and in the activation of leukocytes.

Adenosine Diphosphate Ribose↗
PubMed2000

Trp12, a novel Trp related protein from kidney.

A novel member of the transient receptor potential (Trp) family of ion channels, Trp12, was identified. The Trp12 mRNA is abundantly expressed in mouse kidney and encodes a protein of 871 amino acid residues. Trp12 transfected cells reveal an elevated cytosolic Ca(2+) and respond with a further increase of cytosolic Ca(2+) to perfusion with hypoosmotic solutions. The human orthologue of murine Trp12 was localized on a genomic clone derived from human chromosome 12. It is composed of 15 translated exons. The intron placement within that primary structure does not correlate with the previously postulated splice sites in transcripts encoding the stretch-inhibitable channel which shares a high degree of amino acid sequence identity with Trp12 and the vanilloid receptor type 1.

Amino Acid Sequence↗
PubMed2003

Lessons from peppers and peppermint: the molecular logic of thermosensation.

Sensory neurons report a wide range of temperatures, from noxious heat to noxious cold. Natural products that elicit psychophysical sensations of hot or cold, such as capsaicin or menthol, were instrumental in the discovery of thermal detectors belonging to the transient receptor potential (TRP) family of cation channels. Studies are now beginning to reveal how these channels contribute to thermosensation and how chemical signaling pathways, such as those activated by tissue injury, alter thermal sensitivity through TRP channel modulation. Analysis of TRP channel expression among sensory neurons is also providing insight into how thermal stimuli are encoded by the peripheral nervous system.

Animals↗
PubMed2005

Discovery of potent, orally available vanilloid receptor-1 antagonists. Structure-activity relationship of N-aryl cinnamides.

The vanilloid receptor-1 (TRPV1 or VR1) is a member of the transient receptor potential (TRP) family of ion channels and plays a role in regulating the function of sensory nerves. A growing body of evidence demonstrates the therapeutic potential of TRPV1 modulators, particularly in the management of pain. As a result of our screening efforts, we identified (E)-3-(4-tert-butylphenyl)-N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)acrylamide (1), an antagonist that blocks the capsaicin-induced and pH-induced uptake of (45)Ca(2+) in TRPV1-expressing Chinese hamster ovary cells with IC(50) values of 17 +/- 5 and 150 +/- 80 nM, respectively. In this report, we describe the synthesis and structure-activity relationship of a series of N-aryl cinnamides, the most potent of which (49a and 49b) exhibit good oral bioavailability in rats (F(oral) = 39% and 17%, respectively).

Administration, Oral↗
PubMed1998

The membrane topology of human transient receptor potential 3 as inferred from glycosylation-scanning mutagenesis and epitope immunocytochemistry.

Transient receptor potential (Trp) proteins form ion channels implicated in the calcium entry observed after stimulation of the phospholipase C pathway. Kyte-Doolittle analysis of the amino acid sequence of Trp proteins identifies seven hydrophobic regions (H1-H7) with potential of forming transmembrane segments. A limited sequence similarity to voltage-gated calcium channel alpha1 subunits lead to the prediction of six transmembrane (TM) segments flanked by intracellular N and C termini and a putative pore region between TM5 and TM6. However, experimental evidence supporting this model is missing. Using human Trp 3 to test Trp topology, we now confirm the intracellular nature of the termini by immunocytochemistry. We also demonstrate presence of a unique glycosylation site in position 418, which defines one extracellular loop between H2 and H3. After removal of this site and insertion of ten separate glycosylation sites, we defined two additional extracellular loops between H4 and H5, and H6 and H7. This demonstrated the existence of six transmembrane segments formed of H2-H7. Thus, the first hydrophobic region of Trp rather than being a transmembrane segment is intracellular and available for protein-protein interactions. A site placed in the center of the putative pore region was glycosylated, suggesting that this region may have been luminal and was reinserted into the membrane at a late stage of channel assembly.

Animals↗
PubMed2003

Expression and characterization of human transient receptor potential melastatin 3 (hTRPM3).

Transient receptor potential (TRP) cation-selective channels are an emerging class of proteins that are involved in a variety of important biological functions including pain transduction, thermosensation, mechanoregulation, and vasorelaxation. Utilizing a bioinformatics approach, we have identified the full-length human TRPM3 (hTRPM3) as a member of the TRP family. The hTRPM3 gene is comprised of 24 exons and maps to human chromosome 9q-21.12. hTRPM3 is composed of 1555 amino acids and possesses the characteristic six-transmembrane domain of the TRP family. hTRPM3 is expressed primarily in kidney and, at lesser levels, in brain, testis, and spinal cord as demonstrated by quantitative RT-PCR and Northern blotting. In situ hybridization in human kidney demonstrated that hTRPM3 mRNA expression is predominantly found in the collecting tubular epithelium. Heterologous expression of hTRPM3 in human embryonic kidney cells (HEK 293) showed that hTRPM3 is localized to the cell membrane. hTRPM3-expressing cells exhibited Ca2+ concentration-dependent Ca2+ entry. Depletion of intracellular Ca2+ stores by lowering extracellular Ca2+ concentration and treatment with the Ca2+-ATPase inhibitor thapsigargin or the muscarinic receptor agonist carbachol further augmented hTRPM3-mediated Ca2+ entry. The nonselective Ca2+ channel blocker, lanthanide gadolinium (Gd3+), partially inhibited hTRPM3-mediated Ca2+ entry. These results are consistent with the hypothesis that hTRPM3 mediates a Ca2+ entry pathway that apparently is distinct from the endogenous Ca2+ entry pathways present in HEK 293 cells.

Amino Acid Sequence↗
PubMed2006

Differential mechanisms mediating depressor and diuretic effects of anandamide.

BACKGROUND: Anandamide (AEA), one of the endocannabinoid compounds, has an important regulatory function by serving as an autocrine/paracrine or endocrine factor throughout the body via activation of the cannabinoid receptor 1 (CB1) and/or the transient receptor potential vanilloid type 1 (TRPV1) channels. However, the role of AEA in the regulation of renal excretory function is largely unknown. The present study was designed to test the hypothesis that intrarenal administration of AEA enhances renal excretory function leading to a decrease in blood pressure. METHODS: A metabolically stable analog of AEA, methanandamide (MethA, 300 nmol/kg per min), was infused into the left renal medulla of anesthetized Wistar rats with or without a selective TRPV1 antagonist, capsazepine (Capz, 150 nmol/kg per min) or a selective cannabinoid receptor 1 (CB1) antagonist, AM251 (Am, 150 nmol/kg per min). Ureters were cannulated for collection of urine. A laser-Doppler flowmeter was used to determine the changes of blood flow in the cortex and medulla of the infused kidney. RESULTS: In the absence of the changes in cortical and medullary blood flow, unilateral intramedullary infusion of MethA significantly increased urine flow rate by 64% ipsilaterally and 62% contralaterally without changing sodium excretion when compared to vehicle controls (P < 0.01). Neither Capz nor Am blocked the MethA-induced increases in urine flow rate bilaterally. Intramedullary infusion of MethA significantly decreased mean arterial pressure (MAP) (P < 0.01), which was blocked by Am but not Capz. Denervation of the infused kidney blocked the MethA-induced increases in urine flow rate bilaterally without altering MethA-induced decreases in MAP. CONCLUSIONS: Therefore, our data show that intramedullary infusion of AEA increases urine volume excretion and decreases blood pressure via distinct operational mechanisms. While activation of the CB1 receptor may underlie AEA-induced depressor effects, the diuretic effect of AEA appears to be mediated by neuronal reflex of the kidney, which is not sensitive to blockade of the TRPV1 or CB1 receptor.

Animals↗
PubMed2006

Impaired vasodilation in response to perivascular nerve stimulation in mesenteric arteries of TRPV1-null mutant mice.

BACKGROUND: The role of the transient receptor potential vanilloid type 1 (TRPV1) channels expressed in perivascular sensory nerves in the regulation of vascular reactivity is largely unknown. This study was designed to test the hypothesis that vasodilation induced by electrical field stimulation (EFS) of perivascular sensory nerves is mediated by the TRPV1 via release of sensory neurotransmitters in wild-type (WT) mice, and this effect is abolished in gene-targeted TRPV1-null mutant (TRPV1(-/-)) mice. METHODS: Isolated mesenteric resistance arteries from WT and TRPV1(-/-)) mice were perfused and pretreated with guanethedine and atropine to block sympathetic and parasympathetic nerve activity, respectively. After precontracting with phenylephrine, changes of vascular diameters induced by EFS were monitored in the absence or presence of the TRPV1 receptor antagonist capsazepine; the calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP8-37; or the substance P (SP) receptor antagonist, RP67580. RESULTS: EFS-induced vasodilation was significantly reduced in arteries in TRPV1(-/-)) mice when compared to that of WT mice. Capsazepine and CGRP8-37 attenuated vasodilation induced by EFS in WT but not TRPV1(-/-)) mice. In contrast, RP67580 had no effect on the EFS-induced vasodilation in WT or TRPV1(-/-)) mice. The release of CGRP in the face of EFS challenge was significantly increased in both WT and TRPV1(-/-)) arteries, which was attenuated by capsazepine in WT but not TRPV1(-/-)) arteries. Exogenous CGRP caused dose-dependent vasodilation to a similar degree in WT and TRPV1(-/-)) arteries. CONCLUSIONS: Our data show that in WT mice transmural stimulation of perivascular sensory nerves activates the TRPV1, leading to CGRP release from sensory nerve endings; and blockade of CGRP, but not SP, receptors abolishes TRPV1-mediated vasodilation during EFS. All these effects are impaired in TRPV1(-/-)) mice, indicating that TRPV1 plays a key role in modulating perivascular sensory nerve-mediated vasodilation.

Animals↗
PubMed2006

Ethanol inhibits cold-menthol receptor TRPM8 by modulating its interaction with membrane phosphatidylinositol 4,5-bisphosphate.

Ethanol has opposite effects on two members of the transient receptor potential (TRP) family of ion channels: it inhibits the cold-menthol receptor TRPM8, whereas it potentiates the activity of the heat- and capsaicin-gated vanilloid receptor TRPV1. Both thermosensitive cation channels are critically regulated by the membrane lipid, phosphatidylinositol 4,5-bisphosphate (PIP(2)). The effects of this phospholipid on TRPM8 and TRPV1 are also functionally opposite: PIP(2) is necessary for the activation of TRPM8 but it constitutively inhibits TRPV1. This parallel led us to investigate the possible role of PIP(2) in the ethanol-induced modulation of rat TRPM8, heterologously expressed in HEK293T cells. In this study, we characterize the effects of ethanol (0.1-10%) on whole-cell currents produced by menthol and by low temperature (< 17 degrees C). We show that the inclusion of PIP(2) in the intracellular solution results in a strong reduction in the ethanol-induced inhibition of menthol-evoked responses. Conversely, intracellular dialysis with anti-PIP(2) antibody or with the PIP(2) scavenger, poly L-lysine, enhanced the ethanol-induced inhibition of TRPM8. A 20 min pre-incubation with wortmannin caused a modest decrease in inhibition produced by 1% ethanol, indicating that the ethanol-induced inhibition is not mediated by lipid kinases. These findings suggest that ethanol inhibits TRPM8 by weakening the PIP(2)-TRPM8 channel interaction; a similar mechanism may contribute to the ethanol-mediated modulation of some other PIP(2)-sensitive TRP channels.

Alanine↗
PubMed2003

Group I metabotropic glutamate receptors activate a calcium-sensitive transient receptor potential-like conductance in rat hippocampus.

In CA3 pyramidal neurons from organotypic slice cultures, activation of G(q)-coupled group I metabotropic glutamate receptors (mGluRs) induces a non-selective cationic conductance that enhances excitability. We have found that this response shares several properties with conductances that are mediated by the transient receptor potential (TRP) family of ion channels, including inhibition by La(3+), 2-aminoethoxydiphenylborane (2APB), cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL 12,330A) and a doubly rectifying current-voltage relationship. Stimulation of mGluR1 and mGluR5 converged to activate the TRP-like conductance in a synergistic manner, and activation of either subtype alone produced only a fraction of the normal response. Activation of the cationic current required elevated intracellular Ca(2+). Chelating intracellular Ca(2+) or blocking Ca(2+) entry through voltage-gated Ca(2+) channels attenuated responses to the activation of mGluRs. Conversely, raising intracellular Ca(2+) potentiated mGluR activation of the TRP-like conductance. Under control conditions, blocking G protein activation using intracellular GDPbetaS with or without N-(2, 6-dimethylphenylcarbamoylmethyl) triethylammonium chloride (QX-314) prevented mGluR-mediated activation of the TRP-like conductance. Following G protein blockade, however, the coupling between mGluRs 1 and/or 5 and the TRP-like conductance was rescued by increasing intracellular Ca(2+). This suggests that a G protein-independent signalling pathway is also activated by group I mGluRs. Such a pathway may represent an alternative transduction mechanism to maintain metabotropic responses under conditions where G proteins are functionally uncoupled from their cognate receptors.

Animals↗
PubMed2005

Impaired thermosensation in mice lacking TRPV3, a heat and camphor sensor in the skin.

Environmental temperature is thought to be directly sensed by neurons through their projections in the skin. A subset of the mammalian transient receptor potential (TRP) family of ion channels has been implicated in this process. These "thermoTRPs" are activated at distinct temperature thresholds and are typically expressed in sensory neurons. TRPV3 is activated by heat (>33 degrees C) and, unlike most thermoTRPs, is expressed in mouse keratinocytes. We found that TRPV3 null mice have strong deficits in responses to innocuous and noxious heat but not in other sensory modalities; hence, TRPV3 has a specific role in thermosensation. The natural compound camphor, which modulates sensations of warmth in humans, proved to be a specific activator of TRPV3. Camphor activated cultured primary keratinocytes but not sensory neurons, and this activity was abolished in TRPV3 null mice. Therefore, heat-activated receptors in keratinocytes are important for mammalian thermosensation.

Animals↗
PubMed2006

Chronic metabolic acidosis stimulated transcellular and solvent drag-induced calcium transport in the duodenum of female rats.

Chronic metabolic acidosis results in a negative calcium balance as a result of bone resorption and renal calcium loss. However, reports on the changes in intestinal calcium transport have been controversial. The present investigation therefore aimed to study the effects of chronic metabolic acidosis induced by 1.5% NH(4)Cl administration on the three components of duodenal calcium transport, namely, solvent drag-induced, transcellular active, and passive paracellular components, in rats using an in vitro Ussing chamber technique. The relative mRNA expression of genes related to duodenal calcium transport was also determined. We found that 21-day chronic metabolic acidosis stimulated solvent drag-induced and transcellular active duodenal calcium transport but not passive paracellular calcium transport. Our results further demonstrated that an acute direct exposure to serosal acidic pH, in contrast, decreased solvent drag-induced calcium transport in a pH-dependent fashion but had no effect on transcellular active calcium transport. Neither the transepithelial resistance nor duodenal permeability to Na(+), Cl(-), and Ca(2+) via the passive paracellular pathway were altered by chronic metabolic acidosis, suggesting that widening of the tight junction and changes in the charge-selective property of the tight junction did not occur. Thus the enhanced duodenal calcium transport observed in chronic metabolic acidosis could have resulted from a long-term adaptation, possibly at the molecular level. RT-PCR study revealed that chronic metabolic acidosis significantly increased the relative mRNA expression of duodenal genes associated with solvent drag-induced transport, i.e., the beta(1)-subunit of Na(+)-K(+)-ATPase, zonula occludens-1, occludin, and claudin-3, and with transcellular active transport, i.e., transient receptor potential vanilloid family Ca(2+) channels 5 and 6 and plasma membrane Ca(2+)-ATPase isoform 1b. Total plasma calcium and free ionized calcium and magnesium concentrations were also increased, whereas serum parathyroid hormone and 1alpha,25-dihydroxyvitamin D(3) levels were not changed. The results indicated that 21-day chronic metabolic acidosis affected the calcium metabolism in rats partly through enhancing the mRNA expression of crucial duodenal genes involved in calcium absorption, thereby stimulating solvent drag-induced and transcellular active calcium transport in the duodenum.

Acidosis↗