Biomedical subjects

X F Wang

Publications and source records attributed to X F Wang.

At least 19 recordsLinked to original sources

PubMed2003

Expression, immunolocalization, and functional activity of Na+/H+ exchanger isoforms in mouse endometrial epithelium.

The luminal fluid microenvironment of the uterus is important for sperm capacitation and embryo development. In an attempt to understand the possible role of Na(+)/H(+) exchangers (NHEs) in uterine function, the mRNAs of different NHE isoforms as well as their subcellular localization (apical versus basolateral) and functional activity were investigated in mouse endometrial epithelial cells using reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry, and intracellular pH (pH(i)) measurement techniques. The presence of NHE1, NHE2, and NHE4, but not NHE3 mRNAs were revealed by RT-PCR. Immunostaining showed that NHE1, NHE2, and NHE4 were present in both apical and basolateral membranes. The pH(i) recovery from intracellular acidification was Na(+)-dependent; however, the rate of pH(i) recovery depending on basolateral Na(+) was 12.4 times faster than that depending on apical Na(+). The Na(+)-dependent rate of pH(i) recovery was also inhibited by amiloride, indicating H(+) extrusion through NHEs; however, the amiloride sensitivity of the apical membrane was less than that of the basolateral membrane, suggesting the involvement of different types of NHEs in the two membranes. The results indicate that the basolaterally located NHE1, NHE2, and NHE4, in addition to participating in the homeostatic control of intracellular pH, may play a role in H(+) extrusion in order to achieve transepithelial HCO(3)(-) secretion. The apically located NHEs may be involved in mediating Na(+) absorption as alternatives of or complementary to epithelial Na(+) channels.

Animals↗

PubMed2002

Transforming growth factor beta 1 dysregulation in a human oral carcinoma tumour progression model.

A human oral tumour progression model was established that consists of normal epithelial cells and three cell lines representing stages from dysplastic to metastatic cells. To investigate the impact of exogenous transforming growth factor-beta 1 on this model system, we analysed the responsiveness of those cells to transforming growth factor-beta 1 and explored the potential mechanism underlying the transforming growth factor-beta 1 activity. We found that the growth of all cell types, regardless of their stage of tumour progression, is inhibited by transforming growth factor-beta 1, although to different degrees. Transforming growth factor-beta 1 induced the expression of cyclin-dependent kinase inhibitors p15(INK4B), p21WAF1/(CIP1) and p27(KIP1). In contrast, transforming growth factor-beta 1 was found to stimulate the invasive potential of one cell type that represents the most advanced stage of tumour phenotype, suggesting that the impact of transforming growth factor-beta 1 on functional features of tumour cells other than cellular proliferation may play a significant role in the process of oral tumour progression.

Active Transport, Cell Nucleus↗

PubMed2002

Involvement of Na+-HCO3- cotransporter in mediating cyclic adenosine 3',5'-monophosphate-dependent HCO3- secretion by mouse endometrial epithelium.

The present study investigated the involvement of Na+-HCO3- cotransporter in mediating cAMP-stimulated HCO3- secretion across the cultured mouse endometrial epithelium using the short-circuit current (I(SC)) technique and intracellular pH measurement. Forskolin stimulated a rise in the I(SC), 55.6% and 52.1% of which could be reduced by the removal of extracellular Cl- or by eliminating the contribution of Cl- secretion by bumetanide, an inhibitor of Na+-K+-2Cl- cotransporter, respectively. More than 80% reduction in the forskolin-induced I(SC) was obtained when both Cl- and HCO3- in the bath were removed or in HCO3--free solution with bumetanide, indicating that the I(SC) depended on both Cl- and HCO3-. The presence of the Na+ channel-blocker amiloride in the apical solution did not reduce the forskolin-induced I(SC); however, the I(SC) could be abolished by removing Na+ from the bathing solution, suggesting that the Cl-- and HCO3--dependent I(SC) was also dependent on basolateral Na+. The forskolin-stimulated I(SC) could be reduced 43.6% by removal of HCO3- and 47.9% by a Na+-HCO3--cotransporter inhibitor, dihydrogen-4,4'-didsothiocyanostilbene-2,2'-disulfonic acid (H2DIDS). The inhibitory effect of H2DIDS was observed in Cl--free solution, but not when HCO3- was removed, thus confirming its effect on HCO3--dependent transport. Intracellular pH measurements demonstrated that the recovery from cellular acidification depended on the presence of both basolateral Na+ and HCO3-, further indicating the involvement of Na+-HCO3- cotransporter. Reverse transcription-polymerase chain reaction experiments confirmed the expression of Na+-HCO3- cotransporter in the mouse endometrium. The results suggest that basolaterally located Na+-HCO3- cotransporter is involved in mediating cAMP-stimulated HCO3- secretion across the mouse endometrial epithelium.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed2001

Synergistic outside-in regulation of platelet activation by GPIIb/IIIa ligand-induced conformation and oligomerization.

Full platelet activation with serotonin secretion and thromboxane A(2) (TxA(2)) formation induced by a low dose of thrombin receptor agonist peptide (TRAP) or high dose ADP requires platelet aggregation. This requirement can be replaced by pretreatment of platelets with a combination of reagents including: GPIIb/IIIa inhibitors yielding ligand-induced binding sites (LIBS), either arginine-glycine-aspartate-serine (RGDS) peptide or Ro 43-5054, cytochalasin to disrupt actin filaments and crosslinking by a GPIIb/IIIa mAb (pl-62). Crosslinking is required since Fab fragments of pl-62 do not support activation. Engagement of the Fc receptor by the mAb Fc domain is not required for pl-62 augmentation, since it is not blocked by the anti-Fc receptor mAb, IV-3. Another GPIIb/IIIa inhibitor, Ro 44-9883, not yielding LIBS epitopes, serves as a negative control and shows a requirement for LIBS in addition to crosslinking. Focal adhesion kinase tyrosine phosphorylation induced by TRAP is blocked by these GPIIb/IIIa antagonists, but restored by pl-62 crosslinking independent of LIBS induction. Tyrosine phosphorylation of a peptide comigrating with p38 MAP kinase is also inhibited by these antagonists and restored by pl-62 crosslinking. However, p38 MAP kinase activation by low dose TRAP is not affected by these aggregation inhibitors. Tyrosine phosphorylation of a 34-kDa phosphoprotein in the absence of aggregation or TxA(2) formation was uniquely augmented by Ro 43-5054 but not Ro 44-9883 under the above activation conditions.

Acetates↗

PubMed2001

Inhibition of amiloride-sensitive Na(+) absorption by activation of CFTR in mouse endometrial epithelium.

Previous studies have demonstrated amiloride-sensitive Na(+) absorption under basal conditions and cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl(-) secretion following neurohormonal stimulation in the mouse endometrial epithelium. The present study investigated the inhibition of amiloride-sensitive Na(+) absorption accompanying activation of CFTR in the mouse endometrium using the short-circuit current ( I(sc)) technique. RT-PCR demonstrated the co-expression of CFTR and epithelial Na(+) channels (ENaC) in primary cultured mouse endometrial epithelia and cultured endometrial monolayers exhibited a basal amiloride-sensitive I(sc) of 5.4 +/- 0.6 microA/cm(2). The amiloride-sensitive current fell to 3.1 +/- 0.5 microA/cm(2) after stimulation with forskolin. When the possible contribution of Na(+) absorption to the I(sc) was eliminated by amiloride (1 microM) or Na(+) replacement, the forskolin-induced I(sc) was not reduced, but rather increased significantly compared with that in the absence of amiloride or in Na(+)-containing solutions ( P < 0.02), indicating that the forskolin-induced I(sc) was mediated by Cl(-) secretion, portion of which may be masked by concurrent inhibition of basal Na(+) absorption if the contribution of Na(+) is not eliminated. When the contribution of Cl(-) to the I(sc) was eliminated by diphenylamine 2,2'-dicarboxylic acid (DPC, 2 mM) or Cl(-) replacement, forskolin now decreased, rather than increased the I(sc), demonstrating the inhibition of Na(+) absorption upon stimulation. Our data suggest an interaction between CFTR and ENaC, which may be the underlying mechanism for balancing Na(+) absorption and Cl(-) secretion across the mouse endometrial epithelium.

Amiloride↗

PubMed2001

ATR/ATM-mediated phosphorylation of human Rad17 is required for genotoxic stress responses.

Genotoxic stress triggers the activation of checkpoints that delay cell-cycle progression to allow for DNA repair. Studies in fission yeast implicate members of the Rad family of checkpoint proteins, which includes Rad17, Rad1, Rad9 and Hus1, as key early-response elements during the activation of both the DNA damage and replication checkpoints. Here we demonstrate a direct regulatory linkage between the human Rad17 homologue (hRad17) and the checkpoint kinases, ATM and ATR. Treatment of human cells with genotoxic agents induced ATM/ATR-dependent phosphorylation of hRad17 at Ser 635 and Ser 645. Overexpression of a hRad17 mutant (hRad17AA) bearing Ala substitutions at both phosphorylation sites abrogated the DNA-damage-induced G2 checkpoint, and sensitized human fibroblasts to genotoxic stress. In contrast to wild-type hRad17, the hRad17AA mutant showed no ionizing-radiation-inducible association with hRad1, a component of the hRad1-hRad9-hHus1 checkpoint complex. These findings demonstrate that ATR/ATM-dependent phosphorylation of hRad17 is a critical early event during checkpoint signalling in DNA-damaged cells.

Animals↗

PubMed2001

Pyruvate released by astrocytes protects neurons from copper-catalyzed cysteine neurotoxicity.

We have found previously that astrocytes can provide cysteine to neurons. However, cysteine has been reported to be neurotoxic although it plays a pivotal role in regulating intracellular levels of glutathione, the major cellular antioxidant. Here, we show that cysteine toxicity is a result of hydroxyl radicals generated during cysteine autoxidation. Transition metal ions are candidates to catalyze this process. Copper substantially accelerates the autoxidation rate of cysteine even at submicromolar levels, whereas iron and other transition metal ions, including manganese, chromium, and zinc, are less efficient. The autoxidation rate of cysteine in rat CSF is equal to that observed in the presence of approximately 0.2 microm copper. In tissue culture tests, we found that cysteine toxicity depends highly on its autoxidation rate and on the total amount of cysteine being oxidized, suggesting that the toxicity can be attributed to the free radicals produced from cysteine autoxidation, but not to cysteine itself. We have also explored the in vivo mechanisms that protect against cysteine toxicity. Catalase and pyruvate were each found to inhibit the production of hydroxyl radicals generated by cysteine autoxidation. In tissue culture, they both protected primary neurons against cysteine toxicity catalyzed by copper. This protection is attributed to their ability to react with hydrogen peroxide, preventing the formation of hydroxyl radicals. Pyruvate, but not catalase or glutathione peroxidase, was detected in astrocyte-conditioned medium and CSF. Our data therefore suggest that astrocytes can prevent cysteine toxicity by releasing pyruvate.

Animals↗

PubMed2001

A genetically tractable model of human glioma formation.

Gliomas remain one of the deadliest forms of cancer. Improved therapeutics will require a better understanding of the molecular nature of these tumors. We, therefore, mimicked the most common genetic changes found in grade III-IV gliomas, disruption of the p53 and RB pathways and activation of telomere maintenance and independence from growth factors, through the ectopic expression of the SV40 T/t-Ag oncogene, an oncogenic form of H-ras (H-ras(V12G)), and the human telomerase catalytic subunit hTERT in normal human astrocytes. The resulting cells displayed many of the hallmarks of grade III-IV gliomas, including greatly expanded life span and growth in soft agar and, most importantly, were tumorigenic with pathology consistent with grade III-IV neuroectodermal tumors in mice. This model system will, for the first time, allow the biological significance of selected genetic alterations to be studied in human gliomas.

Animals↗

PubMed2001

An essential role for Mad homology domain 1 in the association of Smad3 with histone deacetylase activity*.

The Smads are a family of sequence-specific DNA-binding proteins that modulate transcription in response to transforming growth factor beta (TGFbeta) by recruiting transcriptional activators like the histone acetyltransferase, p300/CBP, or repressors like the histone deacetylase, HDAC1, to TGFbeta target genes. The association of Smads and HDAC1 is mediated in part by direct binding of Smads to the HDAC1-associated proteins, TG-interacting factor, c-ski, and SnoN. Although ectopic expression of these proteins inhibits Smad-activated transcription, the contribution of histone deacetylase enzymatic activity to transcriptional repression by TGFbeta is unknown. Here, the biological requirements for the interaction between Smads and endogenous histone deacetylase activity are investigated. We identify residues in Mad homology domain 1 of Smad3 that are required for association with histone deacetylase activity. An amino acid change at one of these critical residues does not disrupt the association of Smad3 with c-ski, SnoN, and transforming growth-interacting factor but does abrogate the ability of Smad3 to repress transcription. These findings indicate that the association of Smad3 and histone deacetylase activity relies on additional protein mediators that make contact with Smad3 at its amino terminus. Moreover, these data suggest that the suppressive effect of Smad3 on transcription is dependent upon its association with histone deacetylase enzymatic activity.

Base Sequence↗

PubMed2001

The activity of guanine exchange factor NET1 is essential for transforming growth factor-beta-mediated stress fiber formation.

To examine signaling pathways underlying transforming growth factor-beta (TGF-beta)-mediated changes in cell morphology, we used a microarray system to identify downstream target genes that may play a role in this process. Through this approach, we found that the NET1 gene was induced upon TGF-beta treatment in several cell types. NET1 is a guanine nucleotide exchange factor for RhoA whose activity has been implicated in stress fiber formation. In the Swiss 3T3 cell line, TGF-beta induces NET1 expression, and this correlated with an increase in stress fiber formation. Overexpression of the wild type NET1 gene increases stress fiber formation, and overexpression of a dominant negative NET1 mutant (L392E) prevented TGF-beta dependent increase in stress fiber formation. Furthermore, treatment of the cells with a RhoA kinase inhibitor Y-27632 blocks TGF-beta-induced stress fiber formation. By using a stable cell line expressing dominant negative Smad3, we found that the Smad signaling pathway is essential for the induction of NET1, which in turn leads to the increase of Rho activity. Taken together, those data suggest that induction of NET1 is important for the increase of Rho activity upon TGF-beta treatment, which may represent the critical trigger for a variety of downstream events in different cells. Our results support the presence of a novel signaling pathway by which TGF-beta may regulate the formation of stress fibers and reorganization of cytoskeletal structures.

3T3 Cells↗

PubMed2001

A new noninvasive method for evaluation of coronary endothelial function in hypertensive patients based on change in diameter of the left main coronary artery induced by cold pressor test using echocardiography.

BACKGROUND: Coronary endothelial function is frequently studied by measuring the vasodilator response of coronary arteries to acetylcholine or to cold pressor test by invasive quantitative coronary angiography. Because invasive methods have substantial inherent limitations, studies should attempt to evaluate coronary endothelial function noninvasively. HYPOTHESIS: We attempted to evaluate the accuracy of measurement of the percent change in diameter of the left main trunk induced by cold pressor test with two-dimensional (2-D) echocardiography. Furthermore, we applied this method to the evaluation of coronary artery endothelial function in hypertensive patients. METHODS: We measured the left main trunk diameter in 21 subjects (51 +/- 4 years) before and after cold pressor test using quantitative coronary angiography followed immediately by 2-D echocardiography. The accuracy of measurement of the left main trunk diameter and its percent change by echocardiography was evaluated by comparing the values obtained by the two methods. In addition, using echocardiography, we compared left main trunk diameter responses to cold pressor test in 16 hypertensive patients [51 +/- 5 years (mean +/- standard deviation)] and 16 matched healthy subjects (50 +/- 4 years). RESULTS: Although there was only a weak correlation between the absolute values of the left main trunk diameter measured by the two methods (r = 0.61; p = 0.04), a strong correlation was found between the percent change in diameter measured by the two methods (r = 0.93; p = 0.0001). The percent change in diameter of the left main trunk induced by cold pressor test in hypertensive patients (-3.7 +/- 10.6%) was significantly lower than that in control subjects (13.2 +/- 6.8%, p = 0.0001). CONCLUSIONS: Percent change in diameter of the left main trunk induced by cold pressor test can be evaluated accurately using 2-D echocardiography. Our study showed reduced vasodilation or vasoconstriction of the left main trunk after cold pressor test in hypertensive patients compared with healthy subjects, indicating impaired coronary endothelial function in hypertensive patients. The present echocardiographic method is a potentially useful new noninvasive method for evaluating coronary endothelial function.

Adult↗

PubMed2001

Suppression of ATP-induced Cl(-)secretion by enhanced expression of epithelial Na(+)channels in mouse endometrial epithelium.

We have studied the effect of enhanced expression of epithelial Na(+)channels (ENaC) on the ATP-induced Cl(-)secretion in the mouse epithelium using short-circuit current (I(SC)) and RT-PCR techniques. The amiloride sensitivity of basal current (I(b)) across the cultured endometrial epithelia was found to vary with the magnitude of the I(b), the higher the I(b)the greater its sensitivity to amiloride, indicating possible elevation of ENaC. However, the magnitude of ATP-induced I(SC), previously demonstrated to be mediated by Ca(2+)-activated chloride channel (CaCC), decreased as the amiloride sensitivity of the I(b)increased, suggesting a possible inhibitory effect of elevated expression of ENaC on ATP-mediated chloride secretion. The Matrigel treatment for culturing the endometrial epithelia affected the amiloride sensitivity of the I(b)as well as the ATP-induced I(SC)reversedly. Competitive RT-PCR demonstrated that the expression of both ENaC gamma subunits and CaCC was enhanced in Matrigel-treated cultures. However, the observed reduction in the ATP-induced or CaCC-mediated I(SC)could not be explained by the CaCC expression pattern. These data suggest that inhibition of CaCC function is due to enhanced ENaC expression. Therefore, in addition to interacting with CFTR, ENaC also appears to interact with CaCC in the mouse endometrial epithelium. Physiologically the present findings indicate that enhanced expression of ENaC leads to suppression of other Cl(-)channels, such as CFTR and CaCC, thereby preconditioning the endometrium in favour of overall salt and water absorption as observed during embryo implantation.

Adenosine Triphosphate↗

PubMed2001

The role of Smad3 in mediating mouse hepatic stellate cell activation.

Transforming growth factor beta (TGF-beta) is the most potent profibrogenic mediator in liver fibrosis. Although Smad proteins have been identified as intracellular mediators in the TGF-beta signaling pathway, the function of individual Smad proteins remains poorly understood. The aim of this study was to explore the contribution of Smad3 in mediating TGF-beta responses in a model of acute liver injury in vivo and in culture-activated hepatic stellate cells (HSCs). Wild-type, Smad3 heterozygous or Smad3 homozygous knockout mice were treated with a single intragastric administration of CCl(4). After 72 hours, the induction of hepatic collagen alpha1(I) and alpha2(I) messenger RNA (mRNA) levels in Smad3 knockout mice was only 42% and 64%, respectively, of the levels induced in wild-type mice. However, smooth muscle alpha-actin (alpha-SMA) was expressed at a slightly higher level in livers from knockout mice compared with wild-type mice. In culture-activated HSCs from Smad3 knockout mice, collagen alpha1(I) mRNA was 73% of wild-type HSCs, but alpha-SMA expression was the same. HSCs from knockout mice showed a higher proliferation rate than wild-type HSCs. Smad3-deficient HSCs did not form TGF-beta1-induced Smad-containing DNA-binding complexes. In conclusion, (1) maximal expression of collagen type I in activated HSCs requires Smad3 in vivo and in culture; (2) Smad3 is not necessary for HSC activation as assessed by alpha-SMA expression; (3) Smad3 is necessary for inhibition of proliferation of HSCs, which might be TGF-beta-dependent; and (4) Smad3 is required for TGF-beta1-mediated Smad-containing DNA-binding complex formation in cultured HSCs.

Actins↗

PubMed2001

The loss of Smad3 results in a lower rate of bone formation and osteopenia through dysregulation of osteoblast differentiation and apoptosis.

Smad3 is a well-characterized intracellular effector of the transforming growth factor beta (TGF-beta) signaling pathway and was implicated recently in the potentiation of vitamin D receptor (VDR)-mediated signaling. Given that both TGF-beta and vitamin D are important regulators of bone remodeling, it is expected that Smad3 plays an integral role in normal maintenance of bone. However, the exact mechanisms by which Smad3 functions in bone remodeling are unknown. Here, we show that mice with targeted deletion of Smad3 are osteopenic with less cortical and cancellous bone compared with wild-type littermates. Decreases in bone mineral density (BMD) in Smad3 null mice reflect the inability of osteoblasts to balance osteoclast activity, although osteoclast numbers are normal and vitamin D mediated serum calcium homeostasis is maintained. The osteopenia of Smad3 null mice is attributed to a decreased rate of bone formation associated with increased osteocyte number and apoptosis. These findings are supported by studies with isolated primary osteoblasts that show TGF-beta can no longer inhibit the differentiation of osteoblasts in the absence of Smad3; yet, TGF-beta-stimulated proliferation remains intact. Together these data support a model that a loss of Smad3 increases the osteocyte fate of the osteoblast and decreases the duration of osteoblast function by shortening lifespan, ultimately resulting in osteopenia.

Animals↗

PubMed2001

Enhanced epithelial Na(+) channel (ENaC) activity in mouse endometrial epithelium by upregulation of gammaENaC subunit.

The amiloride-sensitive epithelial Na(+) channel (ENaC), which is made of three different but homologous subunits, controls the rate of transepithelial Na(+) absorption in a variety of epithelia. The present study investigated the functional role of its subunits in regulating ENaC activity, measured as amiloride sensitive short-circuit current (I(SC)), in the mouse endometrial epithelium under different culture conditions. The treatment of the cultured epithelia with aldosterone (1 microM) or culturing cells on filters coated with concentrated Matrigel resulted in an increase in the amiloride-sensitive I(SC). Semiquantitative RT-PCR demonstrated that the expression of alpha and beta subunits was not significantly altered by these treatments, but an increase in the gamma subunit expression was observed. An 11-fold increase, induced by aldosterone, in the expression of the gamma subunit, but not in the alpha and beta subunits, was confirmed by capillary electrophoresis with laser-induced fluorescence (CE-LIF). The treatment of endometrial cells with antisense against the gammaENaC subunit abolished the aldosterone-enhanced amiloride-sensitive I(SC). The results indicated an important role of gammaENaC subunit in determining ENaC activity, and a possible role of the gammaENaC subunit in interacting with CFTR was also discussed.

Absorption↗

PubMed2001

[Comparison of immune responses elicited by recombinant protein and eukaryotic expression plasmid based on histidine rich protein 2 of Plasmodium falciparum].

OBJECTIVE: To identify the immune characteristics of different vaccine prototypes based on HRP2 and to provide experimental evidence for developing P. f. blood stage vaccines. METHODS: BALB/c mice were immunized with recombinant protein TP-HRP2 or eukaryotic expression plasmid pcDNA3.1(-)/HRP2. The kinetics and specificities of antibody responses were analyzed. The proliferation tests of spleen cells were done, and P. f. growth inhibition assays were done with immune sera. RESULTS: The mice immunized with TP-HRP2 in Freund's adjuvant produced high-level and high-specificity antibody response. The antibodies appeared rapidly and lasted for a longer time. Cellular responses were induced simultaneously, and the immune sera could inhibit the development of parasite in IRBCs. The mice immunized with pcDNA3.1(-)/HRP2 produced middle-level antibody response which had some specificity, however, the induction of antibodies required repeated inoculation and a longer duration. Immune cells were well primed and the memorial immune response was obvious but the immune sera had no effect on the growth of P.f. in vitro. CONCLUSION: Both the recombinant protein and plasmid DNA based on HRP2 have different immune characteristics in mice. HRP2 recombinant protein has the potential in practical application.

Animals↗

PubMed2001

[Study on the characters of hydrogen bonds in protein and nucleic acid of the breast cancer tissues].

Some remarkable spectral differences are observed between the normal breast tissues and breast cancer tissues, including those of association pattern and degree of the hydrogen bonds in the protein and nucleic acid biomacromolecules. These differences are found in the relative intensity, absorption position and shape of the characteristic bands: (1) amide I band, stretching vibration bands of N-H group and C-O(H) in the residues of some amino-acids, and (2) the relative intensity of asymmetric stretching vibration of the phosphodiester group in nucleic acid. The hydrogen bond is the major force which maintain and promote the formation of the high structure of protein and nucleic acid. It is possible to diagnose the breast cancer and forecast the possibility of canceration using above spectral characters of the hydrogen bond with other spectral characters.

Amides↗

PubMed2000

Suppression of CFTR-mediated Cl(-) secretion by enhanced expression of epithelial Na(+) channels in mouse endometrial epithelium.

The present study investigated the effect of enhanced expression of epithelial Na(+) channels (ENaC) on the cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl(-) secretion in the mouse endometrium using the short-circuit current technique. The amiloride sensitivity of the basal current of the cultured endometrial epithelia was found to vary with the magnitude of the basal current, the higher the basal current the greater its sensitivity to amiloride, indicating possible elevation of ENaC expression. However, the magnitude of the forskolin-induced Isc, previously demonstrated to be mediated by CFTR, decreased as the amiloride sensitivity of the basal current increased, suggesting a possible inhibitory effect of elevated expression of ENaC on CFTR-mediated Cl(-) secretion. The Matrigel concentration for culturing the endometrial epithelia was found to affect the amiloride sensitivity of the basal current as well as the forskolin-induced Isc in opposite directions. However, competitive RT-PCR demonstrated that the expression of both ENaC and CFTR was enhanced in Matrigel-treated culture, suggesting that the reduced forskolin-induced Isc with enhanced amiloride sensitivity was not due to a reduction in CFTR expression, but rather suppression of CFTR function by enhanced ENaC expression. In addition to the previously demonstrated inhibition of ENaC by activation of CFTR, the present results reveal possible regulation of CFTR by ENaC. The interaction between the two may be one of the underlying mechanisms for balancing Na(+) absorption and Cl(-) secretion across epithelia.

Animals↗