Folic acid transport by mammalian small intestine.

The unidirectional influx of folic acid across the mucosal border of hamster duodenum and rat jejunum was determined. Influx follows saturation kinetics, is sodium-dependent, and is inhibited by methotrexate and is sodium-dependent, and is inhbited by methotrexate and folinic acid in the mucosal bathing solution. In hamster duodenum, the maximal influx is 1.2 nmol/(cm2.h), and the folic acid concentration required to give a half maximal influx (Km) is 7.2 micron.. At mucosal folic acid concentration of 1.5 micron, influx is reduced at least 65% by removal of sodium from the bathing solution. The influx process is significantly inhibited by cyanide and 2,4-dinitrophenol. The possibility was evaluated that the acidic microclimate at the brush border regulates the rate of folic acid transport and that inhibition of transmural transport by sodium-free media, ouabain, and methotrexate is brought about indirectly by an increase in pH of the microclimate. The data favor the alternative concept of a sodium-dependent carrier mechanism for entry of folic acid into the cells. The information presented is consistent with active transport of folic acid by a sodium-gradient mechanism, but additional information will be necessary to substantiate such a model.

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Ascorbic acid transport in mammalian kidney

AJP Renal Physiology ◽

10.1152/ajprenal.1986.250.4.f627 ◽

1986 ◽

Vol 250 (4) ◽

pp. F627-F632 ◽

Cited By ~ 1

Author(s):

R. C. Rose

Keyword(s):

Ascorbic Acid ◽

Brush Border Membrane ◽

Renal Tissue ◽

Metabolic Inhibitors ◽

Bathing Solution ◽

Acid Transport ◽

Low Concentrations ◽

Sodium Dependent ◽

Ascorbic Acid Transport

Ascorbic acid is known to circulate free in the plasma of several species and is therefore filtered in the kidney; reabsorption subsequently takes place and prevents urinary loss. However, no specific mechanism of renal ascorbic acid transport has previously been presented. In the present study, rat and guinea pig kidney were incubated as slices or as isolated tubules in vitro in the presence of low concentrations of [14C]ascorbic acid. The kidneys of both species handle ascorbic acid similarly. Ascorbic acid accumulates in the renal tissue to a concentration three to four times that present in the bathing media. Recently absorbed ascorbic acid diffuses freely from the kidney and is predominantly nonmetabolized during absorption. Uptake is reduced following replacement of bathing solution sodium by lithium or cesium, or when incubation is performed in the presence of metabolic inhibitors or at low temperatures. The results indicate that ascorbic acid is reabsorbed in the kidney by a sodium-dependent active transport mechanism that operates by concentrating ascorbic acid in the cellular fluid. Renal slices and tubules both appear to transport ascorbic acid and galactose across the brush-border membrane; this indicates that the tubular lumens in these preparations are not collapsed or sealed off.

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Ascorbic acid flux across mucosal border of guinea pig and human ileum.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1977.233.5.e374 ◽

1977 ◽

Vol 233 (5) ◽

pp. E374 ◽

Cited By ~ 1

Author(s):

A J Mellors ◽

D L Nahrwold ◽

R C Rose

Keyword(s):

Ascorbic Acid ◽

Guinea Pig ◽

Acid Concentration ◽

Brush Border ◽

Ascorbic Acid Concentration ◽

Ileal Mucosa ◽

Simple Diffusion ◽

Carrier Mechanism ◽

Carrier Mediated Transport ◽

Free Media

The unidirectional influx of L-[14C]ascorbic acid (vitamin C) across the mucosal border of guinea pig and human ileum was determined. Influx follows saturation kinetics, indicating that a carrier mechanism is operative. The maximal influx in guinea pig ileum bathed in Ringer is 140 nmol/cm2-h and the ascorbic acid concentration greater than 6 mM , or when the tissue is bathed in Na-free media, influx is approximately linearly related to the ascorbic acid concentration, and absorption by simple diffusion may predominate. With mucosal ascorbic acid concentration of 0.28 mM, influx is reduced by at least 70% when Na-free media is used; however, influx is not dependent on the intracellular Na concentration. The brush border mechanism appears to be stereospecific and not closely coupled to cellular metabolism. A model of transport is favored that features a carrier-mediated transport mechanism for simultaneous entry of ascorbic acid and Na across the brush border. This model is similar in nature to, but functionally distinct from, the sodium-gradient mechanism postulated to effect sugar and amino acid transport in mammalian ileal mucosa.

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Quantitative requirement for ATP for active transport in isolated renal cells

AJP Cell Physiology ◽

10.1152/ajpcell.1986.251.1.c120 ◽

1986 ◽

Vol 251 (1) ◽

pp. C120-C127 ◽

Cited By ~ 11

Author(s):

N. Tessitore ◽

L. M. Sakhrani ◽

S. G. Massry

Keyword(s):

Atpase Activity ◽

Active Transport ◽

Phosphate Uptake ◽

Quantitative Relationship ◽

Similar Degree ◽

Renal Cells ◽

Stepwise Manner ◽

Sodium Gradient ◽

Sodium Dependent ◽

86Rb Influx

We investigated the quantitative relationship between cellular ATP concentration and Na+-K+-ATPase activity as measured by ouabain-sensitive 86Rb influx in rabbit proximal renal cells. Cellular ATP was reduced in a stepwise manner by rotenone (10(-7) to 10(-5) M) and was increased by 10 mM adenosine. During these maneuvers, ouabain-sensitive 86Rb influx was linearly related to cellular ATP and did not saturate up to 9.9 mM ATP. In contrast, Na+-K+-ATPase activity in membranes prepared from these cells saturated at 2.0 mM ATP at various sodium (10-100 mM) and potassium (4-100 mM) concentrations. Sodium-dependent phosphate uptake and alpha-methylglucoside (alpha-MG) uptake were both inhibited to a similar degree when cellular ATP was reduced. We conclude that 1) the ATP requirement for saturation of Na+-K+-ATPase is higher in intact renal cells than in the membranes, and 2) the uptake of phosphate and alpha-MG are similarly influenced by reduction in ATP. This effect of ATP on phosphate and AMG uptake is most likely an indirect one and is secondary to changes in the sodium gradient across the cell.

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Inhibition of Amino Acid Transport in Rabbit Intestine by p-Chloromercuriphenyl Sulfonic Acid

The Journal of General Physiology ◽

10.1085/jgp.62.2.131 ◽

1973 ◽

Vol 62 (2) ◽

pp. 131-146 ◽

Cited By ~ 42

Author(s):

John F. Schaeffer ◽

Robert L. Preston ◽

Peter F. Curran

Keyword(s):

Transport System ◽

Conformational Changes ◽

Marked Reduction ◽

Sulfhydryl Group ◽

Major Effect ◽

Acid Transport ◽

Michaelis Constant ◽

Saturation Kinetics ◽

Rabbit Intestine ◽

Transport Site

Influx of phenylalanine across the brush border of rabbit intestine is markedly reduced by treatment with 5 mM p-chloromercuriphenyl sulfonate (PCMBS). The effect is rapidly and completely reversed by dithiothreitol. Phenylalanine influx into PCMBS-treated tissue can be competitively inhibited by other neutral amino acids and follows saturation kinetics. PCMBS causes an increase in the apparent Michaelis constant from the value observed in control tissue but does not alter the maximal influx significantly. Treatment of the tissue with PCMBS leads to a significant reduction in the Na-sensitivity of the transport, and a number of results indicate that the major effect of the reagent is to cause a marked reduction in the affinity of the transport system for Na. The transport system can be partially protected against reaction with PCMBS by phenylalanine and tryptophan but not by methionine or norleucine. The results suggest that PCMBS reacts with a sulfhydryl group in the region of the transport site and may alter conformational changes associated with the binding of substrates.

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Changes in folate characteristics and its identification in broccoli (Brassica oleracea Italica) extract fermented by Lactic Acid Bacteria Mixed Culture (LAB)

MATEC Web of Conferences ◽

10.1051/matecconf/201815404001 ◽

2018 ◽

Vol 154 ◽

pp. 04001 ◽

Cited By ~ 1

Author(s):

Yati Maryati ◽

Agustine Susilowati

Keyword(s):

Lactic Acid ◽

Folic Acid ◽

Lactic Acid Bacteria ◽

Brassica Oleracea ◽

Acid Concentration ◽

Ph Value ◽

Starter Culture ◽

Time Interval ◽

Fermentation Time ◽

Total Sugars

Broccoli (Brassica oleracea Italica) was fermented by cultures of lactic acid bacteria (LAB) as a potential source of natural folic acid. This study aimed to evalte characteristic changes and to identify folate compounds from broccoli extract, fermented by mixed LAB cultures (L. bulgaricus, S. thermophulus, L.acidophilus, Bd. bifidum). The formulation of broccoli extract was fermented with variation of LAB starter culture with concentrations of 10 and 20%(v/v), and the change of characteristic of folic acid compound during fermentation (0 to 48 hours) with an interval of 8 hours was evaluated. The results showed that the fermentation of broccoli extract with different concentration of LAB culture had an effect on the concentration of folic acid produced, as well as the change of concentration of folic acid during the fermentation time interval. The optimum condition was obtained based on the highest folic acid concentration of 6.74%, at culture concentration of 20% during 24 hour fermentation with the value of folic acid concentration of 72.11 μg/mL, pH value of 4.29, total sugars of 34.61%, total acids of 0, 97%, dissolved protein of 14.64 mg/mL and total LAB of log 13.02 + 0.05 cfu / ml.

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Amino acid transport in the thermophilic anaerobe Clostridium fervidus is driven by an electrochemical sodium gradient.

Journal of Bacteriology ◽

10.1128/jb.175.7.2060-2066.1993 ◽

1993 ◽

Vol 175 (7) ◽

pp. 2060-2066 ◽

Cited By ~ 29

Author(s):

G Speelmans ◽

B Poolman ◽

W N Konings

Keyword(s):

Amino Acid ◽

Amino Acid Transport ◽

Acid Transport ◽

Sodium Gradient

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ALK Folic Acid Transport and Integrin Signal Induced-Angiogenesis Network in Human Hepatocellular Carcinoma (HCC) by Systems-Theoretical Analysis

Molecular Biology ◽

10.4172/2168-9547.1000102 ◽

2012 ◽

Vol 01 (01) ◽

Author(s):

Lin Wang

Keyword(s):

Hepatocellular Carcinoma ◽

Folic Acid ◽

Theoretical Analysis ◽

Human Hepatocellular Carcinoma ◽

Acid Transport

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alpha-Aminoisobutyric acid transport in rat soleus muscle during endotoxic shock

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1985.248.2.r142 ◽

1985 ◽

Vol 248 (2) ◽

pp. R142-R146 ◽

Cited By ~ 1

Author(s):

M. D. Karlstad ◽

M. M. Sayeed

Keyword(s):

Skeletal Muscle ◽

Salmonella Enteritidis ◽

Endotoxic Shock ◽

Acid Transport ◽

Aminoisobutyric Acid ◽

Control Value ◽

Rat Soleus Muscle ◽

The Difference ◽

Free Media

We studied alpha-aminoisobutyric acid (AIB) transport by skeletal muscle and the effect of insulin and Na+ on the transport process during endotoxic shock. Rats (140–160 g) were injected with Salmonella enteritidis endotoxin (20 mg/kg iv) or saline and killed 5 h later. At that time an elevation of blood lactate and hypoglycemia marked the onset of shock in rats given endotoxin. AIB uptake was measured in isolated soleus muscles in vitro. Total cellular AIB uptake in the endotoxic muscles was 25, 28, and 47% lower than control muscles at 1-, 2-, or 3-h incubations, respectively. Insulin stimulated AIB uptake to a lesser extent in endotoxic muscles (from a basal value of 11.62 +/- 0.29 nmol X g dry wt-1 X 3 h-1 to 15.88 +/- 0.64, 19.10 +/- 1.06, and 18.78 +/- 0.52 at 1, 10, and 100 mU/ml insulin, respectively) than in controls (from 17.07 +/- 0.51 to 27.13 +/- 1.16, 27.25 +/- 0.93, and 29.01 +/- 1.09). Na+-dependent AIB uptake, calculated as the difference between AIB uptake in the presence and absence of Na+, was decreased in the endotoxic muscles to 36% of the control value. Na+-independent AIB uptake (measured in Na+-free media) was the same in control and endotoxic muscles. These results suggest that the decrease in both basal and insulin-stimulated AIB transport was due to the decrease in Na+-dependent AIB transport by skeletal muscle during endotoxic shock.

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Nature of taurodehydrocholic acid uptake in rat hepatocytes

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1988.254.2.g269 ◽

1988 ◽

Vol 254 (2) ◽

pp. G269-G274 ◽

Cited By ~ 1

Author(s):

W. G. Hardison ◽

P. J. Lowe ◽

E. Gosink

Keyword(s):

Membrane Potential ◽

Rat Hepatocytes ◽

Competitive Inhibitor ◽

Acid Uptake ◽

Isolated Rat Hepatocytes ◽

Acid Analogue ◽

Sodium Gradient ◽

Sodium Dependent ◽

Independent Process ◽

Transport Site

We studied uptake into isolated rat hepatocytes of the bile acid analogue taurodehydrocholate (TDHC) over a concentration range of 2.5-4,000 microM. Uptake was mainly by a saturable sodium-dependent process with a Km of approximately 50 microM and a Vmax of 0.036 nmol.s-1.mg protein-1. A lesser sodium-independent process was evident but was linear in the range studied. Both processes were inhibited by incubation at 37 degrees C under nitrogen in the presence of 3 mM sodium cyanide or by incubation at 0 degrees C. A single transport site was suggested by the Eadie-Hofstee plot of TDHC uptake from 2.5 to 750 microM. TDHC was a weak competitive inhibitor of taurocholic acid (TCA) uptake (Ki = 236 microM) but was not itself taken up by the TCA transport site. TCA exhibited moderately potent mixed inhibition of TDHC uptake. Uptake of both compounds was strongly inhibited by bromosulfophthalein (BSP) and Rose Bengal, whereas 0.5 mM alanine uptake was not affected. BSP exhibited a complex pattern of inhibition of TDHC uptake: mixed partial inhibition. Degree of inhibition of both TDHC and TCA uptake did not increase as BSP concentrations were increased from 50 to 100 microM. BSP did not exert its inhibitory effects by alteration of membrane potential or sodium gradients; 50 microM BSP changed membrane potential less than 10% and sodium gradient not at all. The data indicate that despite close structural analogy between TDHC and TCA, the two compounds are taken up by different sodium-dependent mechanisms. Nonetheless, the similar qualitative and quantitative effects of BSP on their uptakes suggests the mechanisms are related.

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