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Voltage-clamp studi...
Voltage-clamp studies of the Na+/glucose cotransporter cloned from rabbit small intestine.
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- Birnir, Bryndis (författare)
- Department of Physiology, UCLA School of Medicine
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Loo, D D (författare)
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Wright, E M (författare)
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(creator_code:org_t)
- 1991
- 1991
- Engelska.
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Ingår i: Pflügers Archiv. - 0031-6768 .- 1432-2013. ; 418:1-2, s. 79-85
- Relaterad länk:
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https://urn.kb.se/re...
Abstract
Ämnesord
Stäng
- Inward Na+ currents associated with the cloned intestinal Na+/glucose cotransporter expressed in Xenopus oocytes have been studied using the two-microelectrode voltage-clamp method. The steady-state current/voltage relations showed voltage-dependent (Vm from +20 to -75 mV) and relatively voltage-independent (Vm from -75 to -150 mV) regions. The apparent Imax for Na+ and glucose increased with negative membrane potentials, and the apparent K0.5 for glucose (K(Glc)0.5) depended on Vm and [Na]o. Increasing [Na]o from 7 to 110 mmol/l had the same effect in decreasing K(Glc)0.5 from 0.44 to 0.03 mmol/l as increasing the Vm from -40 to -150 mV. The I/V curves under saturating conditions (20 mmol/l external sugars and 110 mmol/l [Na]o) were identical for D-glucose, D-galactose, alpha-methyl D-glucopyranoside and 3-O-methyl D-glucoside. The specificity of the cotransporter for sugars was: D-glucose, D-galactose, alpha-methyl D-glucopyranoside greater than 3-O-methyl D-glucoside much greater than D-xylose greater than D-allose much greater than D-mannose. Ki for phlorizin (approximately 10 mumol/l) was independent of Vm at saturating [Na]o. We conclude that a variety of sugars are transported by the cloned Na+/glucose cotransporter at the same maximal rate and that membrane potential affects both the maximal current and the apparent K0.5 of the cotransporter for Na+ and glucose.
Ämnesord
- MEDICIN OCH HÄLSOVETENSKAP -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)
- MEDICAL AND HEALTH SCIENCES -- Basic Medicine -- Physiology (hsv//eng)
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