scholarly journals Alanine Efflux across the Serosal Border of Turtle Intestine

1972 ◽  
Vol 60 (6) ◽  
pp. 720-734 ◽  
Author(s):  
J.J. Hajjar ◽  
R.N. Khuri ◽  
Peter F. Curran
Keyword(s):  
Amino Acid ◽  
Intestinal Cells ◽  
Mucosal Cell ◽  
Transport Mechanisms ◽  
Acid Transport ◽  
Free Medium ◽  
Cell Border ◽  
Alanine Transport ◽  
Acid Extrusion ◽  
Amino Acid Flux

The exit of alanine across the serosal border of the epithelial cells of turtle intestine was measured by direct and indirect techniques. A decrease or an increase in cell Na did not affect the amino acid flux from cell to serosal solution. Cells loaded with Na and alanine did not exhibit any extrusion of alanine when their serosal membranes were exposed to an Na-free medium containing alanine. However, substantial amino acid extrusion was observed across the mucosal cell border under similar conditions. Although alanine flux across the serosal membrane appeared to be Na-independent, it showed a tendency toward saturation as cellular alanine concentration was elevated. The results are consistent with the postulate that the serosal and mucosal membranes of intestinal cells are asymmetrical with respect to amino acid transport mechanisms. The serosal membrane appears to have an Na-independent carrier-mediated mechanism responsible for alanine transport while transport across the mucosal border involves an Na-dependent process.

Active Transport of α-Aminoisobutyric Acid by the Isolated Midgut of Hyalophora Cecropia

1972 ◽  
Vol 56 (1) ◽  
pp. 167-172
Author(s):  
SIGNE NEDERGAARD
Keyword(s):  
Amino Acid ◽  
Active Transport ◽  
Opposite Direction ◽  
Amino Acid Transport ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Acid Transport ◽  
Active Process ◽  
Aminoisobutyric Acid ◽  
Amino Acid Flux

1. The α-aminoisobutyric acid flux from lumen to blood of the isolated Cecropia midgut is around 17 µmole/h, while the amino acid flux in the opposite direction is on average 0.3 µmole/h. 2. The amino acid uptake is inhibited by lack of oxygen. It is suggested that the amino acid transport from lumen to blood is an active process. 3. The amino acid uptake is inhibited by short-circuiting the midgut potential, indicating that there is no direct correlation between the active transport of potassium and the uptake of the amino acid by the midgut.

scholarly journals Electrogenic Na+-dependentl-alanine transport in the lizard duodenum. Involvement of systems A and ASC

2001 ◽  
Vol 280 (3) ◽  
pp. R612-R622
Author(s):  
Virtudes Medina ◽  
Antonio Lorenzo ◽  
Mario Dı́az
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
Short Circuit ◽  
Duodenal Mucosa ◽  
Neutral Amino Acid ◽  
Acid Transport ◽  
Transport Activity ◽  
System A ◽  
Alanine Transport ◽  
Gallotia Galloti

l-Alanine transport across the isolated duodenal mucosa of the lizard Gallotia galloti has been studied in Ussing chambers under short-circuit conditions. Net l-alanine fluxes, transepithelial potential difference (PD), and short-circuit current ( Isc) showed concentration-dependent relationships. Na+-dependent l-alanine transport was substantially inhibited by the analog α-methyl aminoisobutyric acid (MeAIB). Likewise, MeAIB fluxes were completely inhibited byl-alanine, indicating the presence of system A for neutral amino acid transport. System A transport activity was electrogenic and exhibited hyperbolic relationships for net MeAIB fluxes, PD, and Isc, which displayed similar apparent K m values. Na+-dependentl-alanine transport, but not MeAIB transport, was partially inhibited by l-serine and l-cysteine, indicating the participation of system ASC. This transport activity represents the major pathway for l-alanine absorption and seemed to operate in an electroneutral mode with a negligible contribution to the l-alanine-induced electrogenicity. It is concluded from the present study that the active Na+-dependent l-alanine transport across the isolated duodenal mucosa of Gallotia galloti results from the independent activity of systems A and ASC for neutral amino acid transport.

AMINO ACID TRANSPORT IN YEAST AND EFFECTS OF NYSTATIN

1963 ◽  
Vol 41 (1) ◽  
pp. 397-407 ◽  
Author(s):  
E. Stachiewicz ◽  
J. H. Quastel
Keyword(s):  
Fatty Acids ◽  
Amino Acid ◽  
Calcium Ions ◽  
Amino Acid Transport ◽  
Protective Action ◽  
Yeast Cells ◽  
Acid Transport ◽  
Free Medium ◽  
Complete Protection ◽  
Normal Cells

Nystatin, an antifungal antibiotic, inhibits the accumulation, by yeast cells, of glycine, leucine, arginine, and alanine at concentrations that have no effect on the respiration of the cells. The uptake of glycine by yeast cells that have been preincubated with nystatin and then suspended in a nystatin-free medium is much lower than that of normal cells. The longer the preincubation with nystatin, the greater is the inhibition of glycine uptake. Nystatin produces two distinct effects. At concentrations below 0.8 μg/ml, nystatin inhibits glycine or arginine uptake. At concentrations from 0.8 to 2.0 μg/ml, it causes an efflux of previously accumulated glycine or arginine. Fatty acids, such as oleic, linoleic, stearic, or palmitic acid, can protect the yeast cell from the action of nystatin. The presence of citrate or versene abolishes the protective action of these fatty acids. Calcium ions also protect the cell from the action of nystatin. The concentration of calcium ions giving complete protection depends upon the nystatin concentration. The implications of these facts on amino acid transport in yeast are discussed.

AMINO ACID TRANSPORT IN YEAST AND EFFECTS OF NYSTATIN

1963 ◽  
Vol 41 (2) ◽  
pp. 397-407 ◽  
Author(s):  
E. Stachiewicz ◽  
J. H. Quastel
Keyword(s):  
Fatty Acids ◽  
Amino Acid ◽  
Calcium Ions ◽  
Amino Acid Transport ◽  
Protective Action ◽  
Yeast Cells ◽  
Acid Transport ◽  
Free Medium ◽  
Complete Protection ◽  
Normal Cells

Nystatin, an antifungal antibiotic, inhibits the accumulation, by yeast cells, of glycine, leucine, arginine, and alanine at concentrations that have no effect on the respiration of the cells. The uptake of glycine by yeast cells that have been preincubated with nystatin and then suspended in a nystatin-free medium is much lower than that of normal cells. The longer the preincubation with nystatin, the greater is the inhibition of glycine uptake. Nystatin produces two distinct effects. At concentrations below 0.8 μg/ml, nystatin inhibits glycine or arginine uptake. At concentrations from 0.8 to 2.0 μg/ml, it causes an efflux of previously accumulated glycine or arginine. Fatty acids, such as oleic, linoleic, stearic, or palmitic acid, can protect the yeast cell from the action of nystatin. The presence of citrate or versene abolishes the protective action of these fatty acids. Calcium ions also protect the cell from the action of nystatin. The concentration of calcium ions giving complete protection depends upon the nystatin concentration. The implications of these facts on amino acid transport in yeast are discussed.

Characterisation of Amino Acid Transport in Red Blood Cells of a Primitive vertebrate, the Pacific Hagfish (Eptatretus Stouti)

1990 ◽  
Vol 154 (1) ◽  
pp. 355-370 ◽  
Author(s):  
DARON A. FINCHAM ◽  
MICHAEL W. WOLOWYK ◽  
JAMES D. YOUNG
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Red Blood Cells ◽  
Amino Acid Transport ◽  
Blood Cells ◽  
Red Cells ◽  
Acid Transport ◽  
Intracellular Amino Acid ◽  
Alanine Transport ◽  
The Pacific

Intracellular amino acid levels and the characteristics of amino acid transport were investigated in red blood cells of a primitive vertebrate, the Pacific hagfish (Eptatretus stouti Lockington). In contrast to red cells from euryhaline teleosts and elasmobranchs, which contain high concentrations of β-amino acids, those from hagfish exhibited an intracellular amino acid pool (approx. lOOmmoll−1cell water) composed almost entirely of conventional aαamino acids. Red cell:plasma distribution ratios for individual amino acids ranged from 219, 203 and 173 for alanine, αaminonbutyrate and proline, respectively, to 11 and 13 for lysine and arginine. Corresponding distribution ratios for Na+, K+ and Cl− were 0.043, 21 and 0.32, respectively. The cellular uptake of amino acids, with the exception of Lproline and glycine, was Na+-independent. Compared with mammalian and avian red cells, those from hagfish exhibited 104-fold higher rates of L-alanine transport. Uptake of this amino acid from the extracellular medium was concentrative, but occurred as a 1:1 exchange with intracellular amino acids. The L-alanine transport mechanism was identified as an asc-type system on the basis of its Na+ independence and selectivity for neutral amino acids of intermediate size. A volume-sensitive amino acid channel, which is found in both euryhaline teleosts and in elasmobranchs, is absent from hagfish red cells.

Effects of insulin and exercise on amino acid transport in rat skeletal muscle

1994 ◽  
Vol 266 (2) ◽  
pp. C524-C530 ◽  
Author(s):  
P. A. King
Keyword(s):  
Skeletal Muscle ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Acute Exercise ◽  
Acid Transport ◽  
Rat Skeletal Muscle ◽  
Plasma Membrane Vesicles ◽  
System A ◽  
Alanine Transport ◽  
Glutamine Transport

In the present study, the initial rates of amino acid transport by isolated rat skeletal muscle plasma membrane vesicles were investigated. This approach facilitates the study of the transport of naturally occurring amino acids independent of the effects of cellular metabolism. Alanine and glutamine influxes were measured using a rapid filtration technique. Transport was examined in the presence and absence of Na and the properties of membranes from control, insulin-treated, or acutely exercised rats were studied. Both alanine and glutamine were transported by Na-dependent processes. The values for maximum rate of transport (Vmax) for Na-dependent alanine and glutamine transport were 203 and 224 pmol.mg-1.s-1, respectively. The K1/2 values were 2.9 mM alanine and 1.9 mM glutamine. The Vmax for Na-dependent alanine transport was increased by insulin treatment of the animal and by acute exercise. 2-(Methylamino)-isobutyric acid (MeAIB) partially inhibited the control Na-dependent alanine influx and completely inhibited the increase due to insulin or exercise treatment, indicating the importance of both system A and a non-system A, Na-dependent carrier for alanine transport. The Vmax for Na-dependent MeAIB uptake was also increased by insulin or exercise treatments of the rats. Unlike alanine, Na-dependent glutamine transport was not affected by insulin.

Sign in / Sign up

Export Citation Format

Share Document