Lanthanide-stimulated glucose and proline transport across rabbit intestinal brush-border membranes

Stevens, Bruce R.; Kneer, Christine

doi:10.1016/0005-2736(88)90290-8

Cited by 11 publications

(9 citation statements)

References 13 publications

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“…Abscissa: concentration of Na + (mM). The curves shown are the results of non-linear regression analyses of the control and Eu 3+ data for individual points according to a one-site binding hyperbolic model; the underlying kinetic parameters were as follows: control, K m = 103 mM (confidence limits: 68, 157) and V max = 1.0 pmol · mg protein -1 · min -1 (0.66, 1.7); Eu 3+ , K m = 701 mM (605, 814) and V max = 1.1 pmol · mg protein -1 · min -1 (0.58, 2.0) rabbit renal (Birnir et al 1987) and intestinal (Stevens and Kneer 1988) brush border membrane vesicles, replacement of Na + by La 3+ decreased (but did not abolish) the activity of the Na + /proline (renal and intestinal) and Na + /glucose (intestinal) cotransporters, whereas Eu 3+ and Sm 3+ caused marked stimulation of proline or glucose uptake. For the 5-HTT and DAT in this study, only Eu 3+ , one of the most effective of the lanthanides in replacing Na + for the Na + / glucose and Na + /proline cotransporters, was examined.…”

Section: Discussionmentioning

confidence: 99%

“…In either situation, an increase in the Cl -concentration in the solutions containing the lanthanide salts compared with those containing NaCl and/or LiCl is unavoidable and this is a factor which should be considered in interpreting the results. In previous studies of the Na + /glucose and Na + /proline cotransporters, either equimolar replacement of Na + by lanthanide with addition of varying amounts of mannitol to maintain isotonicity (Birnir et al 1987;Stevens and Kneer 1988) or equiosmolar replacement by the lanthanide (Birnir et al 1990) was used. Eu 3+ was more effective as a replacement ion for Na + when an equimolar replacement was made (Birnir et al 1987;Stevens and Kneer 1988) than when an equiosmolar replacement was made (Birnir et al 1990).…”

Section: Discussionmentioning

confidence: 99%

“…In previous studies of the Na + /glucose and Na + /proline cotransporters, either equimolar replacement of Na + by lanthanide with addition of varying amounts of mannitol to maintain isotonicity (Birnir et al 1987;Stevens and Kneer 1988) or equiosmolar replacement by the lanthanide (Birnir et al 1990) was used. Eu 3+ was more effective as a replacement ion for Na + when an equimolar replacement was made (Birnir et al 1987;Stevens and Kneer 1988) than when an equiosmolar replacement was made (Birnir et al 1990). Hence, in this study, two groups were included for each transporter, one where equiosmolar replacement was made under isotonic conditions and a second group where all solutions were hypertonic (by the addition of 100 mM LiCl to the solutions with the monovalent cations) and Na + was replaced on an equimolar basis.…”

Section: Discussionmentioning

confidence: 99%

“…The rabbit (Hediger et al 1987) and human (Hediger et al 1989) Na + /glucose cotransporters have been cloned and sequenced and appear to have 12 transmembranes regions with intracellular N-and C-termini. The effects of replacement of Na + by other ions have been examined on various members of this family of transporters: the Na + /proline cotransporter in rabbit renal (Birnir et al 1987) and intestinal (Stevens and Kneer 1988) brush-border membranes; the Na + /glucose cotransporter in rabbit intestinal brush-border membranes (Stevens and Kneer 1988) and the Na + /glucose cotransporter expressed in transfected COS-7 cells (Birnir et al 1990). The studies showed that some trivalent lanthanides can substitute for Na + ions, although other monovalent or divalent cations cannot substitute for Na + (Birnir et al 1987;Stevens and Kneer 1988;Birnir et al 1990).…”

Section: Introductionmentioning

confidence: 99%

“…The effects of replacement of Na + by other ions have been examined on various members of this family of transporters: the Na + /proline cotransporter in rabbit renal (Birnir et al 1987) and intestinal (Stevens and Kneer 1988) brush-border membranes; the Na + /glucose cotransporter in rabbit intestinal brush-border membranes (Stevens and Kneer 1988) and the Na + /glucose cotransporter expressed in transfected COS-7 cells (Birnir et al 1990). The studies showed that some trivalent lanthanides can substitute for Na + ions, although other monovalent or divalent cations cannot substitute for Na + (Birnir et al 1987;Stevens and Kneer 1988;Birnir et al 1990). It has been known for more than 20 years that substitution of Na + ions by other monovalent cations (such as Li + or choline + ) results in loss of activity of the monoamine transporters for noradrenaline (Bogdanski and Brodie 1966;Keller and Graefe 1979), 5-HT (Sneddon 1969) and dopamine (Harris and Baldessarini 1973).…”

Section: Introductionmentioning

confidence: 99%

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Lanthanides inhibit the human noradrenaline, 5-hydroxytryptamine and dopamine transporters

Bryan-Lluka

Bönisch

1997

Naunyn-Schmiedeberg's Arch Pharmacol

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Transporters for the monoamine neurotransmitters, including noradrenaline, 5-hydroxytryptamine [5-HT] and dopamine, have twelve transmembrane spanning regions and cotransport Na+ and Cl- ions. Another family of Na(+)-dependent transporters is that containing the Na+/glucose and Na+/proline cotransporters that are found in the epithelial cells of renal and intestinal brush border membranes. It has been shown that various trivalent lanthanides can substitute for Na+ for transport of glucose and proline. The aim of this study was to determine the effects of lanthanides on the activities of the human noradrenaline, 5-HT and dopamine transporters. Cultured cells were incubated for 2 min with 10 nM 3H-noradrenaline (SK-N-SH-SY5Y human neuroblastoma cells), 3H-5-HT (JAR human placental choriocarcinoma cells) or 3H-dopamine (COS-7 cells transfected with the cDNA of the human dopamine transporter). Specific amine uptake was determined as the difference between accumulation of the amine in the cells in the absence and presence of a corresponding uptake inhibitor. Under both isotonic (150 mM NaCl or LiCl or 90 mM lanthanide salt) and hypertonic (150 mM NaCl +100 mM LiCl, 250 mM LiCl or 150 mM lanthanide salt) conditions, replacement of Na+ by Li+, La3+, Eu3+ or Sm3+ abolished the specific uptake of noradrenaline in SK-N-SH-SY5Y cells and replacement of Na+ by Li+ or Eu3+ decreased the specific uptake of 5-HT in JAR cells by 94-100% and that of dopamine in transfected COS-7 cells by 95-99%. The direct effects of Eu3+ (with Na+ present) on the human noradrenaline transporter in SK-N-SH-SY5Y cells were also examined. Eu3+ inhibited noradrenaline uptake into the cells (IC50 2.6 mM) and nisoxetine binding to crude membranes of SK-N-SH-SY5Y cells (IC50 4.7 mM) with similar potencies. Further experiments showed that 4.5 mM EuCl3 in the presence of 150 mM Na+ caused a 3.5-fold increase in the K(m) of noradrenaline and no change in the maximal rate of noradrenaline uptake. EuCl3 (4.5 mM) also caused a pronounced inhibition of the Na(+)-dependent stimulation of noradrenaline uptake by SK-N-SH-SY5Y cells. It can be concluded from these data that, in contrast with the Na+/glucose and Na+/proline cotransporters, the lanthanides cannot substitute for Na+ in the transport of substrates by the monoamine neurotransmitter transporters and that the lanthanides inhibit the latter transporters by interacting with sites of the transporters involved in amine and Na+ binding.

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Section: Discussionmentioning

confidence: 99%