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Tetro N, Moushaev S, Shmuel M, Eyal S. Antiseizure medications and fetal nutrients: Effects on choline transporters in a human placental cell line. Epilepsia 2021; 62:1451-1459. [PMID: 33890297 DOI: 10.1111/epi.16905] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 03/30/2021] [Accepted: 03/31/2021] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Many nutrients essential to the fetus and for proper function of the placenta itself cannot freely diffuse across membrane barriers, and their transplacental transfer depends on transporters. Our previous studies provided evidence for altered expression of transporters for folic acid in trophoblasts exposed to antiseizure medications (ASMs). The goal of the current study was to explore the effects of older and newer ASMs on the expression and function of uptake transporters for choline, which interacts with folate at pathways for methyl group donation. METHODS BeWo cells were incubated for 2 or 5 days with valproate (42, 83, or 166 µg/ml), carbamazepine (6 or 12 µg/ml), levetiracetam (10 or 30 µg/ml), lamotrigine (3 or 12 µg/ml), lacosamide (5, 10, or 20 µg/ml), or their vehicles (n = 6/treatment group). Quantitative polymerase chain reaction (PCR) analysis was utilized to study the effects of ASMs on the transcript levels of the choline transporters SLC44A1 (CTL1) and SLC44A2 (CTL2). Transporter protein expression in valproate-treated cells was assessed by western blot analysis. Choline and acetylcholine were quantified in cell lysates by a choline/acetylcholine assay kit. RESULTS Compared with controls, valproate and levetiracetam at high therapeutic concentrations (83 and 30 µg/ml, respectively) lowered choline transporter transcript levels by up to 42% and 26%, and total choline levels by 20% and 21%, respectively (p < .05). At 83 μg/ml, valproate additionally reduced CTL1 and CTL2 protein expression, by 39 ± 21% and 61 ± 13% (mean ± SD), respectively (p < .01). Carbamazepine reduced SLC44A1 transcript levels, whereas lacosamide modestly decreased the expression of SLC44A2. Lamotrigine did not alter choline transporter expression. SIGNIFICANCE Antiseizure medications, particularly at high therapeutic concentrations, can interfere with the placental uptake of choline. In line with current knowledge from pregnancy registries and clinical studies, the present in vitro findings further support careful adjustment of maternal ASM doses during pregnancy.
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Affiliation(s)
- Nino Tetro
- School of Pharmacy, Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Sonia Moushaev
- School of Pharmacy, Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Miri Shmuel
- School of Pharmacy, Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Sara Eyal
- School of Pharmacy, Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
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Yan J, Jiang X, West AA, Perry CA, Malysheva OV, Devapatla S, Pressman E, Vermeylen F, Stabler SP, Allen RH, Caudill MA. Maternal choline intake modulates maternal and fetal biomarkers of choline metabolism in humans. Am J Clin Nutr 2012; 95:1060-71. [PMID: 22418088 DOI: 10.3945/ajcn.111.022772] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND In 1998 choline Adequate Intakes of 425 and 450 mg/d were established for nonpregnant and pregnant women, respectively. However, to our knowledge, no dose-response studies have been conducted to evaluate the effects of pregnancy or maternal choline intake on biomarkers of choline metabolism. OBJECTIVE We sought to quantify the effects of pregnancy and maternal choline intake on maternal and fetal indicators of choline metabolism. DESIGN Healthy pregnant (n = 26; 27 wk gestation) and nonpregnant (n = 21) women were randomly assigned to receive 480 or 930 mg choline/d for 12 wk. Fasting blood samples and placental tissue and umbilical cord venous blood were collected and analyzed for choline and its metabolites. RESULTS Regardless of the choline intake, pregnant women had higher circulating concentrations of choline (30%; P < 0.001) but lower concentrations of betaine, dimethylglycine, sarcosine, and methionine (13-55%; P < 0.001). Obligatory losses of urinary choline and betaine in pregnant women were ∼2-4 times as high (P ≤ 0.02) as those in nonpregnant women. A higher choline intake yielded higher concentrations of choline, betaine, dimethylglycine, and sarcosine (12-46%; P ≤ 0.08) in both pregnant and nonpregnant women without affecting urinary choline excretion. The higher maternal choline intake also led to a doubling of dimethylglycine in cord plasma (P = 0.002). CONCLUSION These data suggest that an increment of 25 mg choline/d to meet the demands of pregnancy is insufficient and show that a higher maternal choline intake increases the use of choline as a methyl donor in both maternal and fetal compartments. This trial was registered at clinicaltrials.gov as NCT01127022.
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Affiliation(s)
- Jian Yan
- Division of Nutritional Science, Cornell University, Ithaca, NY 14583, USA
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3
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Caudill MA. Pre- and postnatal health: evidence of increased choline needs. ACTA ACUST UNITED AC 2010; 110:1198-206. [PMID: 20656095 DOI: 10.1016/j.jada.2010.05.009] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 03/01/2010] [Indexed: 11/18/2022]
Abstract
Choline, a micronutrient found in food, serves as the starting material for several important metabolites that play key roles in fetal development, particularly the brain. Although human beings' requirement for choline is unknown, an Adequate Intake level of 425 mg/day was established for women with upward adjustments to 450 and 550 mg/day during pregnancy and lactation, respectively. The importance of choline in human development is supported by observations that a human fetus receives a large supply of choline during gestation; pregnancy causes depletion of hepatic choline pools in rats consuming a normal diet; human neonates are born with blood levels that are three times higher than maternal blood concentrations; and large amounts of choline are present in human milk. The development of the central nervous system is particularly sensitive to choline availability with evidence of effects on neural tube closure and cognition. Existing data show that the majority of pregnant (and presumably lactating) women are not achieving the target intake levels and that certain common genetic variants may increase requirements for choline beyond current recommendations. Because choline is not found in most varieties of prenatal vitamins (or regular multivitamins), increased consumption of choline-rich foods may be needed to meet the high pre- and postnatal demands for choline.
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Affiliation(s)
- Marie A Caudill
- Cornell University, Division of Nutritional Sciences, 228 Savage Hall, Ithaca, NY, USA.
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Prouillac C, Lecoeur S. The Role of the Placenta in Fetal Exposure to Xenobiotics: Importance of Membrane Transporters and Human Models for Transfer Studies. Drug Metab Dispos 2010; 38:1623-35. [DOI: 10.1124/dmd.110.033571] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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5
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Cohn BR, Joe BN, Zhao S, Kornak J, Zhang VY, Iman R, Kurhanewicz J, Vahidi K, Yu J, Caughey AB, Swanson MG. Quantitative metabolic profiles of 2nd and 3rd trimester human amniotic fluid using (1)H HR-MAS spectroscopy. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2009; 22:343-52. [PMID: 19779747 PMCID: PMC4852483 DOI: 10.1007/s10334-009-0184-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 08/21/2009] [Accepted: 09/08/2009] [Indexed: 11/26/2022]
Abstract
Object To establish and compare normative metabolite concentrations in 2nd and 3rd trimester human amniotic fluid samples in an effort to reveal metabolic biomarkers of fetal health and development. Materials and methods Twenty-one metabolite concentrations were compared between 2nd (15–27 weeks gestation, N = 23) and 3rd (29–39 weeks gestation, N = 27) trimester amniotic fluid samples using 1H high resolution magic angle spinning (HR-MAS) spectroscopy. Data were acquired using the electronic reference to access in vivo concentrations method and quantified using a modified semi-parametric quantum estimation algorithm modified for high-resolution ex vivo data. Results Sixteen of 21 metabolite concentrations differed significantly between 2nd and 3rd trimester groups. Betaine (0.00846±0.00206 mmol/kg vs. 0.0133±0.0058 mmol/kg, P <0.002) and creatinine (0.0124±0.0058 mmol/kg vs. 0.247±0.011 mmol/kg, P <0.001) concentrations increased significantly, while glucose (5.96±1.66 mmol/kg vs. 2.41±1.69 mmol/kg, P <0.001), citrate (0.740±0.217 mmol/kg vs. 0.399±0.137 mmol/kg, P <0.001), pyruvate (0.0659±0.0103 mmol/kg vs. 0.0299±0.286 mmol/kg, P <0.001), and numerous amino acid (e.g. alanine, glutamate, isoleucine, leucine, lysine, and valine) concentrations decreased significantly with advancing gestation. A stepwise multiple linear regression model applied to 50 samples showed that gestational age can be accurately predicted using combinations of alanine, glucose and creatinine concentrations. Conclusion These results provide key normative data for 2nd and 3rd trimester amniotic fluid metabolite concentrations and provide the foundation for future development of magnetic resonance spectroscopy (MRS) biomarkers to evaluate fetal health and development.
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Affiliation(s)
- Brad R. Cohn
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
| | - Bonnie N. Joe
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
| | - Shoujun Zhao
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
| | - John Kornak
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
- Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA
| | - Vickie Y. Zhang
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
| | - Rahwa Iman
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
| | - John Kurhanewicz
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
| | - Kiarash Vahidi
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
| | - Jingwei Yu
- Department of Laboratory Medicine, University of California, San Francisco, CA, USA
| | - Aaron B. Caughey
- Department of Obstetrics & Gynecology, University of California, San Francisco, CA, USA
| | - Mark G. Swanson
- Department of Radiology & Biomedical Imaging, University of California, 1600 Divisadero Street, Room C-250, Box 1667, San Francisco, CA 94115, USA
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Lee NY, Choi HM, Kang YS. Choline transport via choline transporter-like protein 1 in conditionally immortalized rat syncytiotrophoblast cell lines TR-TBT. Placenta 2009; 30:368-74. [PMID: 19246089 DOI: 10.1016/j.placenta.2009.01.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 01/20/2009] [Accepted: 01/22/2009] [Indexed: 11/25/2022]
Abstract
Choline is an essential nutrient for phospholipids and acetylcholine biosynthesis in normal development of fetus. In the present study, we investigated the functional characteristics of choline transport system and inhibitory effect of cationic drugs on choline transport in rat conditionally immortalized syncytiotrophoblast cell line (TR-TBT). Choline transport was weakly Na(+) dependent and significantly influenced by extracellular pH and by membrane depolarization. The transport process of choline is saturable with Michaelis-Menten constants (K(m)) of 68microM and 130microM in TR-TBT 18d-1 and TR-TBT 18d-2 respectively. Choline uptake in the cells was inhibited by unlabeled choline and hemicholinium-3 as well as various organic cations including guanidine, amiloride and acetylcholine. However, the prototypical organic cation tetraethylammonium and cimetidine showed very little inhibitory effect of choline uptake in TR-TBT cells. RT-PCR revealed that choline transporter-like protein 1 (CTL1) and organic cation transporter 2 (OCT2) are expressed in TR-TBT cells. The transport properties of choline in TR-TBT cells were similar or identical to that of CTL1 but not OCT2. CTL1 was also detected in human placenta. In addition, several cationic drugs such as diphenhydramine and verapamil competitively inhibited choline uptake in TR-TBT 18d-1 with K(i) of 115microM and 55microM, respectively. Our results suggest that choline transport system, which has intermediate affinity and weakly Na(+) dependent, in TR-TBT seems to occur through a CTL1 and this system may have relevance with the uptake of pharmacologically important organic cation drugs.
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Affiliation(s)
- N-Y Lee
- College of Pharmacy, Sookmyung Women's University, Seoul, Republic of Korea
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7
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Kang YS, Lee HA, Lee NY. Regulation of Choline Transport by Oxidative Stress at the Blood-Brain Barrier In Vitro Model. Biomol Ther (Seoul) 2008. [DOI: 10.4062/biomolther.2008.16.1.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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8
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Moon EY. Serum Deprivation Enhances Apoptotic Cell Death by Increasing Mitochondrial Enzyme Activity. Biomol Ther (Seoul) 2008. [DOI: 10.4062/biomolther.2008.16.1.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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Friesen RW, Novak EM, Hasman D, Innis SM. Relationship of dimethylglycine, choline, and betaine with oxoproline in plasma of pregnant women and their newborn infants. J Nutr 2007; 137:2641-6. [PMID: 18029477 DOI: 10.1093/jn/137.12.2641] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Choline and glycine are inter-related through their roles in methyl metabolism. Choline is metabolized to betaine, which donates a methyl group to homocysteine to form methionine, also generating dimethylglycine, which is further metabolized to glycine. Choline is transported across the placenta and is higher in fetal than maternal plasma. Placental glycine transfer, however, is limited and poor glycine status has been suggested in preterm infants. Insufficient glycine for glutathione (GSH) synthesis results in increased metabolism of gamma-glutamyl cysteine to 5-oxoproline. We measured plasma 5-oxoproline as a metabolic indicator to address whether choline, via dimethylglycine, contributes physiologically relevant amounts of glycine in pregnancy. Blood was collected from healthy term pregnant women and their newborn infants at delivery (n = 46) and nonpregnant healthy women (n = 19) as a reference group. Plasma choline, betaine, dimethylglycine, homocysteine, methionine, and 5-oxoproline were quantified by HPLC-tandem MS. Plasma choline was 45% higher, but betaine was 63% lower and dimethylglycine was 28% lower in pregnant than nonpregnant women (P < 0.01). Higher white blood cell choline dehydrogenase messenger RNA levels in a random subset of pregnant (n = 8) than nonpregnant women (n = 7) (P < 0.01) suggest increased betaine and dimethylglycine turnover rather than decreased synthesis. Plasma choline, betaine, and dimethylglycine were higher (P < 0.001) in fetal plasma (36.4 +/- 13, 29.4 +/- 1.0, and 2.44 +/- 0.12 micromol/L, respectively) than maternal plasma (15.3 +/- 0.42, 14.1 +/- 0.6 and 1.81 +/- 0.12 micromol/L, respectively). Concentrations of 5-oxoproline and dimethylglycine were inversely (P < 0.05) correlated in maternal (Spearman rho = -0.35) and fetal plasma (Spearman rho = -0.32), suggesting that choline, via dimethylglycine, contributes glycine for GSH synthesis in human development.
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Affiliation(s)
- Russell W Friesen
- Nutrition Research Program, Child and Family Research Institute, University of British Columbia, Vancouver, Canada V5Z 4H4
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Fujita T, Shimada A, Okada N, Yamamoto A. Functional characterization of Na+-independent choline transport in primary cultures of neurons from mouse cerebral cortex. Neurosci Lett 2006; 393:216-21. [PMID: 16239069 DOI: 10.1016/j.neulet.2005.09.069] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 09/09/2005] [Accepted: 09/27/2005] [Indexed: 11/23/2022]
Abstract
We report here the functional characteristics of Na+-independent choline transport system in primary cultures of neurons from mouse cerebral cortex. Na+-independent choline transport was saturable with a Michaelis constant (Kt) of 26.7+/-1.2 microM and a maximal velocity (Vmax) of 1.04+/-0.02 nmol/mg protein/10 min. Choline uptake was significantly influenced by extracellular pH and by membrane depolarization. This uptake system was inhibited by various organic cations including unlabeled choline, guanidine, diphenhydramine and the choline analog hemicholinium-3. However, the prototypical organic cation tetraethylammonium and cimetidine showed very little affinity for the Na+-independent choline uptake system in neurons. These results indicate that mouse cerebrocortical neurons express a Na+-independent, high-affinity choline transport system. RT-PCR revealed that choline transporter-like protein 1 (CTL1) and its spliced variant CTL1a, which have been reported to be novel Na+-independent choline transporter, are expressed in mouse cerebrocortical neurons. The Na+-independent transport properties of choline in mouse neurons is similar or identical to that of CTL1 and/or CTL1a. This choline transport system seems to have relevance not only for neuronal physiology but also for the uptake of pharmacologically important organic cation drugs.
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Affiliation(s)
- Takuya Fujita
- Department of Biochemical Pharmacology, Kyoto Pharmaceutical University, Misasagi, Kyoto 607-8414, Japan.
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Müller J, Born I, Neubert RH, Brandsch M. Apical uptake of choline and cationic drugs in epithelial cell lines derived from human placenta. Placenta 2005; 26:183-9. [PMID: 15708119 DOI: 10.1016/j.placenta.2004.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/03/2004] [Indexed: 10/26/2022]
Abstract
Many cationic drugs are administered during pregnancy and might enter the fetal circulation by transplacental passage. This study was performed to characterize the apical uptake of choline and several cationic drugs at cultured epithelial cells of the human placenta. Total uptake of [3H]choline in BeWo cells was H(+)-independent and to 65% Na(+)-independent. Uptake rates into both cell lines were saturable with Michaelis-Menten constants (Kt) of 108 microM (BeWo) and 206 microM (JEG-3), respectively. Cationic drugs such as etilefrine, clonidine, ranitidine, diphenhydramine, imipramine and butylscopolamine strongly inhibited the [3H]choline uptake in BeWo cells and in JEG-3 cells, with Ki values ranging from 0.18 to 3.3 mM. In contrast, tetraethylammonium had only little inhibitory effect on [3H]choline uptake. Using high-performance capillary electrophoresis for quantitative analyses, uptake of etilefrine and diphenhydramine into JEG-3 or BeWo cells was measured. Diphenhydramine was transported into JEG-3 cells in a saturable manner with a Kt value of 0.75 mM. In the presence of sodium, diphenhydramine uptake at BeWo cells was inhibited to 69% by the addition of 50 mM choline chloride. Like choline uptake, total diphenhydramine uptake was to 68% Na(+)-independent in BeWo cells. We conclude that in addition to choline, several cationic drugs, in particular diphenhydramine, are taken up by placental epithelial cells from the maternal blood by carrier-mediated processes. Etilefrine, clonidine, ranitidine, diphenhydramine and butylscopolamine interact with the Na(+)-independent placental choline transport system.
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Affiliation(s)
- J Müller
- Membrane Transport Group, Biozentrum of the University, Martin-Luther-University Halle-Wittenberg, D-06120 Halle, Germany
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Hoffmann K, Grafe F, Wohlrab W, Neubert RH, Brandsch M. Functional characterization of a high-affinity choline transport system in human keratinocytes. J Invest Dermatol 2002; 119:118-21. [PMID: 12164933 DOI: 10.1046/j.1523-1747.2002.01801.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This study was performed to characterize the mechanism of choline transport into human keratinocytes. Uptake of [3H]choline was measured both in the HaCaT cell line and in native keratinocytes. Uptake in HaCaT cells was linear with time at least up to 10 min. There was little dependence of choline transport on sodium. Choline uptake was slightly stimulated by extracellular H+ with the pH optimum being 7.5. The uptake rate was saturable and indicated participation of a single transport system (Kt = 14.8 +/- 1.0 micro M, Vmax = 1.0 +/- 0.01 nmol per 10 min per mg protein). The choline uptake into HaCaT cells was inhibited by unlabeled choline, hemicholinium-3, and acetylcholine. The prototypical organic cation tetraethylammonium showed very little affinity for the choline uptake system in these cells. Several cationic drugs such as diphenhydramine, clonidine, and atropine also interacted with the transport system. Choline uptake in normal keratinocytes was very similar to that in HaCaT cells with respect to substrate specificity and affinity. We conclude that keratinocytes express a Na+ independent, high-affinity choline transport system. This system accepts many pharmacologically important organic cations as substrates. It is similar or identical to the choline carrier described in intestinal epithelial cells and in endothelial cells of the blood-brain barrier. The choline carrier seems to have relevance not only for the uptake of cationic drugs into the keratinocytes but also for the biosynthesis of skin lipids.
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Affiliation(s)
- Kathrin Hoffmann
- Department of Pharmacy, Institute of Pharmaceutics and Biopharmaceutics, Biozentrum of the University, Martin-Luther-University Halle-Wittenberg, D-06120 Halle/Saale, Germany
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Abstract
Placental transfer of maternal calcium (Ca(2+)) is a crucial process for fetal development although the biochemical mechanisms responsible for this transfer are largely unknown. We have investigated the characteristics of Ca(2+)uptake by the human placental trophoblast cell line BeWo. The kinetics studies revealed an active extracellular Ca(2+)uptake by BeWo cells, which was rapid in the first 2 min (initial velocity (V(i)) of 4.17+/-0.25 nmol/mg/min), and showed a subsequent plateau. Uptake experiments performed at V(i)with increasing concentrations of Ca(2+)resulted in a typical saturation curve (K(m)of 0.54+/-0.07 m m and V(max)of 7.07+/-0.28 nmol/mg protein/min). Lowering the pH of the incubation medium from 7.4 to 5.5 led to Ca(2+)uptake inhibition of 40-50 per cent. The presence of voltage-sensitive (l -type) Ca(2+)channels in BeWo cells was demonstrated by Western blot. Therefore, the implication of such channels in basal Ca(2+)uptake of BeWo cells was investigated. Cell depolarization with extracellular high potassium concentration (40 m m), and hyperpolarization with extracellular high chloride concentration (60 m m) or with valinomycin (10 microm) did not influence the basal Ca(2+)uptake of BeWo cells. The L-type Ca(2+)channel modulators (Bay K 8644 and Nitrendipine) had no effect on the Ca(2+)uptake. An antagonist of receptor-mediated, store-operated and voltage-gated Ca(2+)channels (SKF-96365) also did not modulate the Ca(2+)uptake of BeWo cells. Therefore, our results indicate that the basal Ca(2+)uptake of BeWo cells is inhibited by lowering pH of the incubation medium, is voltage independent, and is not influenced by l -type Ca(2+)channel and capacitative Ca(2+)conductance modulators.
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Affiliation(s)
- R Moreau
- Laboratoire de Physiologie materno-foetale, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Québec, Canada, H3C 3P8
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Abstract
BeWo choriocarcinoma cells were cultured onto solid microcarrier beads, packed into columns and superfused. Unidirectional influx of l -phenylalanine (l -phe) and l -leucine (l -leu) across the microvillous border of the cells was studied using a rapid paired-tracer dilution technique. Influx of l -phe and l -leu comprised both saturable and non-saturable components. K(m)values for l -phe and l -leu were 0.57+/-0.01 m m and 0.05+/-0.01 m m, respectively, with V(max)values of 120.4+/-0.5 nmol/mg/min and 41. 7+/-0.2 nmol/mg/min. Non-saturable uptake components were 29.0+/-0.1 nmol/mg/m m and 37.9+/-0.1 nmol/mg/min/m m respectively. l -leu uptake was found to be sodium-independent. The uptake of l -[(3)H]phe was strongly inhibited (90-100 per cent) by unlabelled l -phe, d -phe, l -leu or 2-aminoendobicyclo-[2,2, 1]-heptane-2-carboxylic acid (BCH) but not by l -arginine (l -arg) or methyl alpha-aminoisobutric acid (Me-AIB). Pre-incubation of Bewo cultures for 24 h in the presence of an additional 1.2 m ml -phe (simulating maternal phenylketonuria) significantly reduced both the K(m)and V(max)components of l -phe influx. l -arg (2 m m) had no effect on l -leu influx whereas 2 m ml -phe completely inhibited saturable l -leu influx. These data suggest that the microvillous border of differentiated BeWo cells transport large neutral amino acids predominantly via system L rather than by B(0) or y(+)L transporters.
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Affiliation(s)
- B M Eaton
- Department of Maternal and Fetal Medicine, Imperial College School of Medicine, Chelsea and Westminster Hospital, London, UK.
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Utoguchi N, Audus KL. Carrier-mediated transport of valproic acid in BeWo cells, a human trophoblast cell line. Int J Pharm 2000; 195:115-24. [PMID: 10675689 DOI: 10.1016/s0378-5173(99)00398-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The biochemical mechanisms mediating the rapid distribution of valproic acid across placenta are not precisely known. We have characterized valproic acid transport by the human trophoblast using the human choriocarcinoma cell line, BeWo. The uptake of [14C]valproic acid by BeWo cells was found to be saturable and blocked by pre-exposure to the metabolic inhibitors, sodium azide and 2,4-dinitrophenol. Valproic acid uptake by the BeWo cells was also inhibited by the protonophore, carbonylcyanide p-trifluoromethoxyphenylhydrazone, but not anion exchange inhibitor. Selected monocarboxylic acids inhibited the uptake of [14C]valproic acid by BeWo cells, whereas dicarboxylic acids did not alter the uptake process. Analysis of Lineweaver-Burk plots of valproic acid uptake in the presence of benzoic acid, a marker for the monocarboxylic acid transporter, revealed a competitive process for uptake. In transcellular transport experiments, the permeation of [14C]valproic acid from the apical-to-basal side of the monolayers was significantly greater than the permeation from basal-to-apical side. Additionally, the permeation of [14C]valproic acid from apical-to-basal side was inhibited by monocarboxylic acids and not dicarboxylic acids. The results provide biochemical evidence of a proton-dependent, saturable, and asymmetric transport system, presumed to be a monocarboxylic acid transporter, for valproic acid in a human trophoblast model.
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Affiliation(s)
- N Utoguchi
- Department of Pharmaceutical Chemistry, School of Pharmacy, The University of Kansas, Lawrence, KS 66047, USA
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