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Bongarzone S, Sementa T, Dunn J, Bordoloi J, Sunassee K, Blower PJ, Gee A. Imaging Biotin Trafficking In Vivo with Positron Emission Tomography. J Med Chem 2020; 63:8265-8275. [PMID: 32658479 PMCID: PMC7445742 DOI: 10.1021/acs.jmedchem.0c00494] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The water-soluble vitamin biotin is essential for cellular growth, development, and well-being, but its absorption, distribution, metabolism, and excretion are poorly understood. This paper describes the radiolabeling of biotin with the positron emission tomography (PET) radionuclide carbon-11 ([11C]biotin) to enable the quantitative study of biotin trafficking in vivo. We show that intravenously administered [11C]biotin is quickly distributed to the liver, kidneys, retina, heart, and brain in rodents-consistent with the known expression of the biotin transporter-and there is a surprising accumulation in the brown adipose tissue (BAT). Orally administered [11C]biotin was rapidly absorbed in the small intestine and swiftly distributed to the same organs. Preadministration of nonradioactive biotin inhibited organ uptake and increased excretion. [11C]Biotin PET imaging therefore provides a dynamic in vivo map of transporter-mediated biotin trafficking in healthy rodents. This technique will enable the exploration of biotin trafficking in humans and its use as a research tool for diagnostic imaging of obesity/diabetes, bacterial infection, and cancer.
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Affiliation(s)
- Salvatore Bongarzone
- School of Biomedical Engineering & Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - Teresa Sementa
- School of Biomedical Engineering & Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - Joel Dunn
- School of Biomedical Engineering & Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - Jayanta Bordoloi
- School of Biomedical Engineering & Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - Kavitha Sunassee
- School of Biomedical Engineering & Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - Philip J Blower
- School of Biomedical Engineering & Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - Antony Gee
- School of Biomedical Engineering & Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
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Abstract
Significant progress has been made in our understanding of the biochemical, physiological and nutritional aspects of the water-soluble vitamin biotin (vitamin H). It is well know now that biotin plays important roles in a variety of critical metabolic reactions in the cell, and thus, is essential for normal human health, growth and development. This is underscored by the serious clinical abnormalities that occur in conditions of biotin deficiency, which include, among other things, growth retardation, neurological disorders, and dermatological abnormalities (reviewed in 1). Studies in animals have also shown that biotin deficiency during pregnancy leads to embryonic growth retardation, congenital malformation and death (Watanabe 1983; Cooper and Brown 1958; Mock et al. 2003; Zempleni and Mock 2000). The aim of this chapter is to provide coverage of current knowledge of the biochemical, physiological, and clinical aspects of biotin nutrition. Many sections of this chapter have been the subject of excellent recent reviews by others (Wolf 2001; McMahon 2002; Mock 2004; Rodriguez-Melendez and Zempleni 2003; Said 2004; Said et al. 2000; Said and Seetheram 2006), and thus, for more information the reader is advised to consider these additional sources.
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Affiliation(s)
- Hamid M Said
- University of California-School of Medicine, Irvine, CA, USA,
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Subramanian VS, Subramanya SB, Said HM. Chronic alcohol exposure negatively impacts the physiological and molecular parameters of the renal biotin reabsorption process. Am J Physiol Renal Physiol 2011; 300:F611-7. [PMID: 21209005 DOI: 10.1152/ajprenal.00707.2010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Normal body homeostasis of biotin is critically dependent on its renal recovery by kidney proximal tubular epithelial cells, a process that is mediated by the sodium-dependent multivitamin transporter (SMVT; a product of the SLC5A6 gene). Chronic ethanol consumption interferes with the renal reabsorption process of a variety of nutrients, including water-soluble vitamins. To date, however, there is nothing known about the effect of chronic alcohol feeding on physiological and molecular parameters of the renal biotin reabsorption process. We addressed these issues using rats and transgenic mice carrying the human SLC5A6 (P1P2) 5'-regulatory region as an in vivo model systems of alcohol exposure, and cultured human renal proximal tubular epithelial HK-2 cells chronically exposed to alcohol as an in vitro model of alcohol exposure. The [(3)H]biotin uptake results showed that chronic ethanol feeding in rats leads to a significant inhibition in carrier-mediated biotin transport across both renal brush border and basolateral membrane domains. This inhibition was associated with a marked reduction in the level of expression of SMVT protein, mRNA, and heterogenous nuclear RNA (hnRNA). Furthermore, studies with transgenic mice carrying the SLC5A6 5'-regulatory region showed that chronic alcohol feeding leads to a significant decrease in promoter activity. Studies with HK-2 cells chronically exposed to alcohol again showed a marked reduction in carrier-mediated biotin uptake, which was associated with a significant reduction in promoter activity of the human SLC5A6 5'-regulatory region. These findings demonstrate for the first time that chronic ethanol feeding inhibits renal biotin transport and that this effect is, at least in part, being exerted at the transcriptional level.
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Affiliation(s)
- Veedamali S Subramanian
- Departments of Medicine, Physiology, and Biophysics, University of California, Irvine, and Department of Veterans AffairsMedical Center, Long Beach, California, USA
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Roch‐Ramel F, Besseghir K, Murer H. Renal Excretion and Tubular Transport of Organic Anions and Cations. Compr Physiol 2011. [DOI: 10.1002/cphy.cp080248] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Nabokina SM, Subramanian VS, Said HM. Comparative analysis of ontogenic changes in renal and intestinal biotin transport in the rat. Am J Physiol Renal Physiol 2003; 284:F737-42. [PMID: 12620923 DOI: 10.1152/ajprenal.00364.2002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Biotin, an essential water-soluble micronutrient, cannot be synthesized by mammals; rather, it is obtained from exogenous sources via uptake by intestinal epithelia. Renal epithelia reclaim the vitamin that is filtered in the glomeruli. Both epithelia take up biotin via the sodium-dependent multivitamin transporter (SMVT). Little is known about ontogenic regulation of the renal and intestinal biotin transport processes and about the mechanism(s) involved in any such regulation. In this study, we sought to examine and compare ontogenic aspects of the renal and intestinal biotin uptake processes using purified brush-border membrane vesicles (BBMV) isolated from the kidney cortex and jejunum of suckling and adult rats. Clear ontogenic changes were observed in the intestinal biotin uptake process, which were mediated via changes in V(max) and apparent K(m). Parallel changes were also seen in protein, mRNA, and transcription rate of SMVT as indicated by results of Western blotting, RT-PCR, and nuclear run-on assays, respectively. In contrast, biotin uptake by renal BBMV did not show ontogenic changes; i.e., it was similar in suckling and adult rats. Also, the levels of SMVT protein and mRNA were similar in the kidneys of both age groups. These data show that biotin uptake by renal and intestinal epithelial cells responds differently to ontogenic regulation. In addition, the ontogenic changes observed in the intestinal biotin uptake process involve the entry step of the vitamin at the BBM and appear to be mediated via a transcriptional mechanism(s).
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Mardach R, Zempleni J, Wolf B, Cannon MJ, Jennings ML, Cress S, Boylan J, Roth S, Cederbaum S, Mock DM. Biotin dependency due to a defect in biotin transport. J Clin Invest 2002. [DOI: 10.1172/jci0213138] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Mardach R, Zempleni J, Wolf B, Cannon MJ, Jennings ML, Cress S, Boylan J, Roth S, Cederbaum S, Mock DM. Biotin dependency due to a defect in biotin transport. J Clin Invest 2002; 109:1617-23. [PMID: 12070309 PMCID: PMC151007 DOI: 10.1172/jci13138] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2001] [Accepted: 05/14/2002] [Indexed: 11/17/2022] Open
Abstract
We describe a 3-year-old boy with biotin dependency not caused by biotinidase, holocarboxylase synthetase, or nutritional biotin deficiency. We sought to define the mechanism of his biotin dependency. The child became acutely encephalopathic at age 18 months. Urinary organic acids indicated deficiency of several biotin-dependent carboxylases. Symptoms improved rapidly following biotin supplementation. Serum biotinidase activity and Biotinidase gene sequence were normal. Activities of biotin-dependent carboxylases in PBMCs and cultured skin fibroblasts were normal, excluding biotin holocarboxylase synthetase deficiency. Despite extracellular biotin sufficiency, biotin withdrawal caused recurrent abnormal organic aciduria, indicating intracellular biotin deficiency. Biotin uptake rates into fresh PBMCs from the child and into his PBMCs transformed with Epstein Barr virus were about 10% of normal fresh and transformed control cells, respectively. For fresh and transformed PBMCs from his parents, biotin uptake rates were consistent with heterozygosity for an autosomal recessive genetic defect. Increased biotin breakdown was ruled out, as were artifacts of biotin supplementation and generalized defects in membrane permeability for biotin. These results provide evidence for a novel genetic defect in biotin transport. This child is the first known with this defect, which should now be included in the identified causes of biotin dependency.
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Affiliation(s)
- Rebecca Mardach
- Regional Metabolic Service, Kaiser Permanente, Los Angeles, California, USA
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Said HM, Ortiz A, Vaziri ND. Mechanism and regulation of vitamin B(6) uptake by renal tubular epithelia: studies with cultured OK cells. Am J Physiol Renal Physiol 2002; 282:F465-71. [PMID: 11832427 DOI: 10.1152/ajprenal.00267.2001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The kidneys play an important role in regulating vitamin B(6) body homeostasis, but limited information exists regarding the mechanism of pyridoxine uptake by renal epithelial cells, and no study exists on its regulation. To address these issues, we used the renal opossum-derived tubular epithelial (opossum kidney; OK) cells and found pyridoxine uptake to 1) be temperature and energy dependent, 2) be pH dependent, with a higher uptake at alkaline or neutral buffer pH compared with acidic pH, 3) be Na(+) independent, 4) involve a saturable component (apparent Michaelis- Menten constant of 2.40 +/- 0.23 microM), 5) be inhibited by structural analogs, and 6) be amiloride sensitive. Maintaining OK cells in a vitamin B(6)-deficient growth medium (for 48 h) led to a significant upregulation of pyridoxine uptake. This upregulation was found to be specific for pyridoxine, inhibited by cyclohexamide and actinomycin D, reversible, and mediated via an increase in maximal velocity. Pretreating OK cells with modulates of a Ca(2+)/calmodulin-mediated pathway led to a significant downregulation in pyridoxine uptake via inhibition of maximal velocity. These results demonstrate that pyridoxine uptake by renal tubular epithelial OK cells is via a specialized pH-sensitive carrier-mediated mechanism. This mechanism appears to be regulated by extracellular vitamin B(6) levels and an intracellular Ca(2+)/calmodulin-mediated pathway.
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Affiliation(s)
- Hamid M Said
- Veterans Affairs Medical Center, Long Beach, California 90822, USA.
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Wang H, Huang W, Fei YJ, Xia H, Yang-Feng TL, Leibach FH, Devoe LD, Ganapathy V, Prasad PD. Human placental Na+-dependent multivitamin transporter. Cloning, functional expression, gene structure, and chromosomal localization. J Biol Chem 1999; 274:14875-83. [PMID: 10329687 DOI: 10.1074/jbc.274.21.14875] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have cloned the human Na+-dependent multivitamin transporter (SMVT), which transports the water-soluble vitamins pantothenate, biotin, and lipoate, from a placental choriocarcinoma cell line (JAR). The cDNA codes for a protein of 635 amino acids with 12 transmembrane domains and 4 putative sites for N-linked glycosylation. The human SMVT exhibits a high degree of homology (84% identity and 89% similarity) to the rat counterpart. When expressed in HRPE cells, the cDNA-induced transport process is obligatorily dependent on Na+ and accepts pantothenate, biotin, and lipoate as substrates. The relationship between the cDNA-specific uptake rate of pantothenate or biotin and Na+ concentration is sigmoidal with a Na+:vitamin stoichiometry of 2:1. The human SMVT, when expressed in Xenopus laevis oocytes, induces inward currents in the presence of pantothenate, biotin, and lipoate in a Na+-, concentration-, and potential-dependent manner. We also report here on the structural organization and chromosomal localization of the human SMVT gene. The SMVT gene is approximately 14 kilobase pairs in length and consists of 17 exons. The SMVT gene is located on chromosome 2p23 as evidenced by somatic cell hybrid analysis and fluorescence in situ hybridization.
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Affiliation(s)
- H Wang
- Department of Biochemistry & Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912, USA
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10
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Mock DM, Mock NI, Nelson RP, Lombard KA. Disturbances in biotin metabolism in children undergoing long-term anticonvulsant therapy. J Pediatr Gastroenterol Nutr 1998; 26:245-50. [PMID: 9523856 DOI: 10.1097/00005176-199803000-00002] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND In subjects undergoing long-term therapy with carbamazepine and/or phenytoin, reduced plasma concentrations of biotin have been reported. However, the diagnostic value of plasma biotin is unclear, in part because of the presence of significant plasma concentrations of biotin metabolites. Pathologic organic aciduria has also been reported with long-term anticonvulsant therapy, suggesting biotin deficiency, but no mechanism leading to deficiency has yet been determined. METHODS In the current study, we sought to determine whether biotin catabolism was accelerated in children receiving long-term treatment with certain anticonvulsants and to assess biotin status as judged by urinary excretion of biotin and 3-hydroxyisovaleric acid, an organic acid that is an indicator of deficiency of a biotin-dependent enzyme. Seven children treated with carbamazepine and/or phenytoin and six treated with phenobarbital provided untimed urine samples. Sixteen healthy children receiving no anticonvulsants served as controls. Biotin and biotin metabolites were determined by high-performance liquid chromatography/avidin-binding assay. Urinary excretion of 3-hydroxyisovaleric acid was determined using gas chromatography/mass spectrometry. RESULTS Bisnorbiotin excretion was increased significantly in the carbamazepine/phenytoin group and in the phenobarbital group. Biotin sulfoxide excretion was significantly increased in the carbamazepine/phenytoin group but not in the phenobarbital group. 3-Hydroxyisovaleric acid excretion was increased significantly in the carbamazepine/phenytoin group. However, only one child (carbamazepine/phenytoin group) had a decreased urinary excretion of biotin. CONCLUSION These data provide evidence that long-term administration of some anticonvulsants can accelerate biotin catabolism, but the indicators of biotin status conflict.
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Affiliation(s)
- D M Mock
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, USA
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11
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Affiliation(s)
- D L Dyer
- Medical Research Service, Long Beach VA Medical Center, California 90822, USA
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12
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Baur B, Baumgartner ER. Na(+)-dependent biotin transport into brush-border membrane vesicles from human kidney cortex. Pflugers Arch 1993; 422:499-505. [PMID: 8474852 DOI: 10.1007/bf00375078] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Renal reabsorption of biotin was investigated in human kidney by means of the isolated brush-border membrane vesicle technique. Biotin uptake into the vesicles was sodium-dependent producing a typical overshoot when incubated under sodium-gradient conditions (external concentration greater than internal). This effect was not observed in the presence of gradients of KCl, LiCl or choline-chloride, nor in the absence of any salt. Using the K+/valinomycin voltage-clamp method biotin uptake remained uninfluenced, i.e. was electroneutral, whereas glucose uptake (which is known to be electrogenic in kidney of other species) was greatly increased. When biotin transport was investigated as a function of external sodium concentration a stoichiometic coupling factor of 1 for the Na(+)-biotin- cotransport was determined. Increasing the biotin concentration in the incubation medium up to 200 mumol/l led to saturation with the kinetic parameters of 31 mumol/l for the apparent Michaelis constant and 82 nmol g protein-1 30 s-1 for the maximal transport rate. Uptake was not saturable in the concentration range of 0.001-1 mumol/l. Inhibition of the biotin uptake (25 mumol/l) was observed in the presence of 250 mumol/l dethiobiotin, bisnorbiotin, thioctic acid, and probenecid, whereas biocytin, propionic acid, lactic acid, succinic acid, citric acid, ascorbic acid, primidone and carbamazepine had no effect. We conclude that renal biotin reabsorption in human kidney is specifically sodium-dependent, saturable and electroneutral. It therefore fulfills the requirements for a secondary active carrier-mediated transport system. The results suggest that biocytin is not an inhibitor of renal biotin reabsorption.
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Affiliation(s)
- B Baur
- University Children's Hospital, Metabolic Unit, Basel, Switzerland
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14
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Barbarat B, Chambrey R, Podevin RA. Heterogeneity in the effects of membrane potentials on pantothenate and glucose uptakes by rabbit renal apical membranes. J Physiol 1991; 443:79-90. [PMID: 1822544 PMCID: PMC1179831 DOI: 10.1113/jphysiol.1991.sp018823] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
1. Previous studies using renal brush-border membrane vesicles have established that both the pantothenate and the low Km (Michaelis-Menten constant), low Vmax (maximal rate) D-glucose systems have a stoichiometry of 2 Na+: 1 organic molecule. In this study, we compared the mechanisms by which the membrane potential energizes pantothenate and D-glucose uptakes by brush-border membrane vesicles isolated from the whole cortex of rabbit kidney. 2. In the absence of Na+, varying the membrane potential from +60 to -60 mV decreased pantothenate uptake, whereas D-glucose uptake was increased in a linear manner. These results suggested the existence of a conductive pathway for pantothenate in these membranes. They also suggested that the pantothenate free carrier is electroneutral, while the glucose free carrier is negatively charged. 3. In the presence of an inwardly directed Na+ gradient, varying the membrane potential from +60 to -60 mV increased Na(+)-dependent pantothenate influx linearly. In contrast, a shift from +60 to +40 mV in the membrane potential had no influence on Na(+)-dependent D-glucose influx, whereas influx was a linear function of the membrane potential from +40 to -60 mV, indicating that there is a threshold membrane potential required for membrane potential-dependent D-glucose movement to occur. 4. Kinetic studies revealed that the effect of membrane potential on pantothenate uptake is through changes in the Km, while Vmax was unchanged. On the other hand, the membrane potential exerted its effect on D-glucose transport solely on the Vmax. 5. Finally, binding studies revealed that membrane potential, both in the presence and absence of a Na+ gradient, elicited effects on phlorizin binding qualitatively similar to those observed for D-glucose transport. 6. Implications of these findings for tubular regulation of these electrogenic secondary active transport systems are discussed.
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Affiliation(s)
- B Barbarat
- Laboratoire de Physiologie et Endocrinologie Cellulaire Rénale, Faculté de Médecine Broussais-Hotel Dieu, Paris, France
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15
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Weiner D, Wolf B. Biotin uptake in cultured hepatocytes from normal and biotin-deficient rats. BIOCHEMICAL MEDICINE AND METABOLIC BIOLOGY 1990; 44:271-81. [PMID: 2288769 DOI: 10.1016/0885-4505(90)90072-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Biotin uptake was studied in isolated cultured hepatocytes of normal and biotin-deficient rats. Biotin uptake was temperature-dependent with respect to physical, but not to chemical, processes, proportional to the exogenous biotin concentration in the medium, independent of pH and sodium ion concentrations of the medium, and uneffected by the presence of structural analogues of biotin or metabolic inhibitors in both normal and biotin-deficient hepatocytes. These results suggest that biotin uptake occurs by a passive, nonmediated, non-energy-dependent mechanism in rat hepatocytes.
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Affiliation(s)
- D Weiner
- Department of Human Genetics, Medical College of Virginia, Richmond 23298
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16
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Said HM, Polenzani L, Khorchid S, Hollander D, Miledi R. Uptake of biotin by native Xenopus laevis oocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 259:C397-401. [PMID: 2399962 DOI: 10.1152/ajpcell.1990.259.3.c397] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The present study examined biotin uptake by Xenopus laevis oocytes in vitro. Uptake of low (0.03 microM) and high (10 microM) concentrations of biotin was linear with time for up to 4 h of incubation and occurred with little initial binding to oocytes. Uptake of biotin was dependent on extracellular Na+ concentration [Na+]o and was severely inhibited when Na+ was replaced by other monovalent cations [choline, tetraethylammonia, Li+, and tris(hydroxymethyl)aminomethane]. The initial rate of biotin uptake was saturable as a function of concentration with an apparent Michaelis constant of 3.9 +/- 0.5 microM and maximum velocity of 1,559 +/- 70 fmol.oocyte-1.h-1. Addition to the incubation medium of biotin structural analogues desthiobiotin and thioctic acid caused significant and concentration-dependent inhibition in the uptake of [3H]biotin. This inhibition was found to be competitive in nature with inhibition constant values of 9 and 17.5 microM. In contrast, neither the structural analogue biocytin nor biotin methyl ester (compounds in which the carboxyl group of the valeric acid moiety is blocked) showed any effect on the uptake of [3H]biotin. Biotin uptake was significantly blocked by the metabolic inhibitors dinitrophenol, cyanide, and azide and by incubation at 4 degrees C. Also, the sulfhydryl group blocker p-(chloromercuri)phenylsulfonate caused significant inhibition in biotin uptake. These results demonstrate that Xenopus oocytes possess an uptake system for biotin in its cell membrane that is Na+, energy, and temperature dependent. These characteristics of biotin uptake are similar to those reported in mammalian cells. It is suggested that Xenopus oocytes might be a useful in vitro model system to study the details of the mechanisms and regulation of biotin movement across biological membranes.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H M Said
- Department of Medicine, School of Medicine, University of California, Irvine 92717
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Spencer PD, Roth KS. On the uptake of biotin by the rat renal tubule. BIOCHEMICAL MEDICINE AND METABOLIC BIOLOGY 1988; 40:95-100. [PMID: 3190927 DOI: 10.1016/0885-4505(88)90109-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Little is known of biotin handling by transporting epithelium. Accordingly, we have examined the characteristics of biotin uptake by rat renal tubular epithelium. Renal cortical slices showed concentrative, temperature-sensitive uptake of biotin. Renal brushborder membrane vesicles exhibited an "overshoot" phenomenon with uptake of 1.9 nM biotin in the presence of a 100 mM NaCl gradient. This overshoot was reduced in magnitude with reduction of the sodium gradient to 50 mM. Biocytin significantly reduced uptake by the vesicles. Concentration-dependent studies yielded an apparent transport Km of 200 nM. We conclude that biotin is actively transported by the rat renal proximal tubule by a system which is at least partially Na+ dependent, and shared by biocytin.
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Affiliation(s)
- P D Spencer
- Department of Pediatrics, Medical College of Virginia, Richmond 23298
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Rose RC. Transport of ascorbic acid and other water-soluble vitamins. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 947:335-66. [PMID: 3285893 DOI: 10.1016/0304-4157(88)90014-7] [Citation(s) in RCA: 137] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- R C Rose
- Department of Surgery, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033
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Barbarat B, Podevin RA. Evidence for distinct pathways in rabbit renal brush-border membrane vesicles for the transport of unsubstituted and alpha-hydroxysubstituted aliphatic monocarboxylic acids. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45173-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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