scholarly journals Search for Carrier-Mediated Transport Systems in the Rat Colon

2003 ◽  
Vol 26 (2) ◽  
pp. 274-277 ◽  
Author(s):  
Shigemitsu Tomei ◽  
Yayoi Hayashi ◽  
Katsuhisa Inoue ◽  
Mayumi Torimoto ◽  
Yuri Ota ◽  
...  
Keyword(s):  
Transport Systems ◽  
Rat Colon ◽  
Carrier Mediated Transport

scholarly journals Kinetic Characterization of Carrier-Mediated Transport Systems for D-Glucose and Taurocholate in the Everted Sacs of the Rat Colon

2003 ◽  
Vol 26 (6) ◽  
pp. 899-901 ◽  
Author(s):  
Shigemitsu Tomei ◽  
Mayumi Torimoto ◽  
Yayoi Hayashi ◽  
Katsuhisa Inoue ◽  
Hiroaki Yuasa ◽  
...  
Keyword(s):  
Transport Systems ◽  
Rat Colon ◽  
Kinetic Characterization ◽  
Carrier Mediated Transport ◽  
Everted Sacs

Transport of L-proline and alpha-methyl-D-glucoside by chicken proximal cecum during development

1991 ◽  
Vol 260 (3) ◽  
pp. G457-G463 ◽  
Author(s):  
M. Moreto ◽  
C. Amat ◽  
A. Puchal ◽  
R. K. Buddington ◽  
J. M. Planas
Keyword(s):  
Surface Area ◽  
Transport Systems ◽  
Independent System ◽  
Passive Components ◽  
Sugar Absorption ◽  
Carrier Mediated Transport ◽  
Lower Capacity ◽  
Nominal Surface ◽  
Passive Influx

We examined the characteristics of amino acid and sugar absorption by the proximal cecum (PC) of chickens during posthatch development. Rates of absorption of L-proline (Pro) and alpha-methyl-D-glucoside (MG) were measured at 2 days, 5 wk, and 13 wk after hatch with an in vitro everted-sleeve method. For each age, pieces of PC and midjejunum were incubated in solutions containing 0.1-50 mM Pro or MG, and the active and passive components of Pro and MG absorption were determined. Five conclusions may be stated. 1) There are two carrier-mediated transport systems for Pro in the PC: a higher capacity Na(+)-dependent system (Vmax between 1.6 and 3.2 nmol.mg-1.min-1), and a lower capacity Na(+)-independent system (Vmax 0.3-0.8 nmol.mg-1.min-1). 2) Whereas both Pro transport systems are present in the PC at 5 and 13 wk, only the Na(+)-dependent system was found at 2 days. Although rates of transport per milligram tissue by the Na(+)-dependent system fell during development, when rates were normalized to nominal surface area, Vmax was significantly higher in the 5-wk-old group than in the other groups. 3) MG transport is by a Na(+)-dependent system. Vmax values (nmol.mg-1.min-1) were 0.32 (2 days), less than 0.43 (5 wk), and = 0.55 (13 wk). These differences were not affected by normalization to surface area. 4) Because at physiological concentrations passive influx of Pro and MG would be negligible, absorption of amino acids and sugars by the PC would be dependent on the presence of carrier-mediated systems.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Absence of Rapid Exchange Component in a Low-Affinity Carrier Transport

1963 ◽  
Vol 46 (4) ◽  
pp. 721-731 ◽  
Author(s):  
Paul G. LeFevre ◽  
Keyword(s):  
Carrier Transport ◽  
Transport Model ◽  
Exchange Process ◽  
Tracer Uptake ◽  
Transport Systems ◽  
Human Red Blood Cells ◽  
Rapid Exchange ◽  
Carrier Mediated Transport ◽  
Net Uptake ◽  
High Concentrations

A previous study showed that human red blood cells equilibrate much less rapidly with D-glucose at moderately high concentrations than with C14-glucose added after the net movement is completed. This had been predicted from a simple reversible mobile-carrier mediated-transport model system suggested by the net monosaccharide transport kinetics in these cells, but is also consistent with the more complex models proposed for certain active transport systems to account for elevation of tracer fluxes of even low-affinity "substrates" when their trans-concentration is raised. The simple model predicts, however, that with any sugar showing a much lower apparent affinity for the reactive sites, such as D-ribose, this phenomenon would not be observed, and tracer equilibration should proceed at approximately the same rate as net uptake. The latter expectation was confirmed experimentally by analyses of the ribose, or radioactivity, content of washed red cells sampled serially during incubation with ribose or C14-ribose in the appropriate mixtures. The tracer ribose movement showed no evidence of a relatively rapid exchange component. The relative rapidity of glucose tracer uptake into cells preloaded with ordinary glucose may therefore more readily be attributed simply to depression of tracer efflux by competition for the saturated reactive sites, than to any action of the trans-concentration on the influx by way of a coupled exchange process.

Effects of phorbol esters on sodium and chloride transport in rat colon

1986 ◽  
Vol 251 (4) ◽  
pp. G509-G517 ◽  
Author(s):  
M. Donowitz ◽  
H. Y. Cheng ◽  
G. W. Sharp
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Transport Systems ◽  
Rat Colon ◽  
Bathing Solution ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Cl Secretion ◽  
Kinase C ◽  
Serosal Surface

To determine the role of protein kinase C in the regulation of active electrolyte transport in rat descending colon, the effects of phorbol dibutyrate (PDB) were studied using the Ussing chamber/voltage-clamp technique. PDB added to the serosal surface increased the short-circuit current in a concentration dependent manner with a EC50 of 3 X 10(-8) M and a maximal effect at 10(-7) M PDB. The effect was not seen with the inactive alpha-phorbol analogue but was reproduced with 1-oleoyl-2-acetylglycerol, a more permeable analogue of diacylglycerol. PDB caused a decrease in mucosal-to-serosal and net fluxes of Na and Cl and an increase in serosal-to-mucosal Cl flux, indicating inhibition of Na and Cl absorption and stimulation of Cl secretion. The PDB-induced increase in Cl secretion was virtually abolished by both indomethacin and ibuprofen, indicating a dependence on arachidonic acid metabolism via the cyclooxygenase pathway. The Cl secretion was inhibited by verapamil and Ca2+-free bathing solution on the serosal surface but not by dantrolene, suggesting the importance of extracellular Ca2+ but not intracellular stored Ca2+ in the PDB-induced secretion. The Cl secretory effect was also inhibited by tetrodotoxin and atropine, suggesting involvement of cholinergic nerves. In contrast, the PDB-induced decrease in Na and Cl absorption was not dependent on metabolites of the cyclooxygenase pathway, not dependent on extracellular Ca2+, and not blocked by tetrodotoxin. It appears likely that protein kinase C is involved in the regulation of rat colonic active Na and Cl absorption and electrogenic Cl secretion but that the pathways involved are different in the two transport systems.

Is leucine an allosteric modulator of the lysine transporter in the intestinal basolateral membrane?

1987 ◽  
Vol 253 (5) ◽  
pp. G637-G642 ◽  
Author(s):  
K. Lawless ◽  
D. Maenz ◽  
C. Cheeseman
Keyword(s):  
Amino Acid ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Low Concentrations ◽  
Carrier Mediated Transport ◽  
Order Of Magnitude ◽  
Dibasic Amino Acid ◽  
Voltage Clamping ◽  
Stimulation Of

The transport of the dibasic amino acid L-lysine was investigated using basolateral membrane vesicles prepared from rat jejunal mucosal scrapings. The majority of the carrier-mediated transport was unaffected by the presence of sodium in the incubation medium, but voltage clamping of the vesicles did increase lysine uptake, indicating an associated movement of charge. Kinetic analysis of lysine influx and efflux showed the system to be symmetrical, but although the Vmax was comparable to other amino acid transport systems in this membrane, the dissociation constant for the overall reaction (KT) was an order of magnitude larger. This low affinity for lysine would explain the relatively slow rate of transport of this amino acid across the basolateral membrane. Competition experiments indicated that this system has a relatively narrow specificity carrying only lysine, arginine, ornithine, and histidine. In contrast the presence of L-leucine caused a marked stimulation of lysine efflux and influx across the vesicles. This effect was observed with leucine concentrations as low as 0.1 microM. It is concluded that although the lysine transport system in the basolateral membrane is slow in its basal state it can be rapidly turned on by the presence of L-leucine. The remarkably low concentrations required to do this suggest a possible allosteric interaction between the transporter and this neutral amino acid.

Carrier-mediated transport of riboflavin in the rat colon

2000 ◽  
Vol 21 (2) ◽  
pp. 77-82 ◽  
Author(s):  
Hiroaki Yuasa ◽  
Masato Hirobe ◽  
Shigemitsu Tomei ◽  
Jun Watanabe
Keyword(s):  
Rat Colon ◽  
Carrier Mediated Transport
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