Active Solute Transport Research Articles

The potential and resistance profile of Necturus gallbladder cells.

Necturus gallbladders were mounted in a modified Ussing chamber and the open circuit potential as well as the IR drop in response to transepithelial current were recorded while passing 2.7 molar KCl-filled microelectrodes in steps of 2–7 μm from the mucosal compartment across the cell into the subepithelial space and back. Using high-resistance electrodes the intracellular electrical potential was found to be independent of the depth of penetration of the electrode into the cell. It averaged −57.9 ±4.5 mV (n=39) with reference to the mucosal solution. Similarly, the resistance between microelectrode tip and mucosal solution was independent of the depth of insertion, indicating that the major part of the IR drop in response to transepithelial currents of 100 μA/cm2 density occured at the cell membranes and that the IR drop inside the cytoplasm was negligibly small. The latter result agrees with quantitative estimates based on the cytoplasmic resistivity of other cells. Using low-resistance microelectrodes the existence of intracellular potential gradients could be simulated. The simultaneous resistance measurements, however, revealed that initial low potential readings must be interpreted as incomplete or leaky impalements. We conclude that active solute and water transport across Necturus gallbladder epithelium does not generate significant intracellular potential gradients.

Single-nephron function and renal oxygen consumption during rapid volume expansion

Isotonic volume expansion reduces net filtrate reabsorption in the proximal tubule while increasing it in Henle's loop. To determine the role oxidative metabolism plays in these processes, experiments were performed on rats initially hydropenic and then rapidly volume expanded with isotonic Ringer solution. Whole-kidney sodium reabsorption, oxygen consumption, and single-nephron function were measured simultaneously. During volume expansion, net renal sodium reabsorption increased concomitantly with a fall in oxygen consumption and a reduction in proximal tubular absolute filtrate reabsorption. The increase in quantity of nonreabsorbed filtrate delivered into the loop of Henle greatly exceeded the amount excreted in the urine. Thus, filtrate reabsorption by the distal nephron segments increased. These data provide evidence that acute volume expansion reduces oxygen-dependent active solute transport in the proximal tubule. The increase noted in distal nephron sodium reabsorption appears nonoxygen dependent, energized by anaerobic glycolysis or occurring passively.

The state of energization of the membrane of Escherichia coli as affected by physiological conditions and colicin K.

The bacterial protein colicin K, when added to sensitive Escherichia coli in the presence of 3,3'-dihexyloxacarbocyanine, cuases a doubling in fluorescence of the probe. Glucose and oxygen cause a decreased fluorescence while anoxia and cyanide cause a rise in fluorescence. These results in conjunction with the work of other laboratories suggest that colicin K causes a depolarization of the transmembrane electrical potential. Fluorescence in the absence of colicin K was relatively independent of KCl, NaCl, and MgCl2 concentrations below 0.1 M. Although colicin K caused rapid efflux of the K+ analogue 86Rb+, the fluorescence rise was only partially blocked by 0.13 M KCl. The level of fluorescence caused by the action of colcin K was inversely proportional to the logarithm of the concentration of MgCl2 over the range of 2 muM to 4 mM. This suggests that a Nernst electrochemical potential for an anion can counteract a membrane depolarization caused by colcin. After colcin K action, the fluorescence of the carbocyanine could be further increased by anoxia or cyanide. The distribution of the weak base dimethyloxazolidinedione indicated that the pH in the interior of aerobic E. coli supplied with lactate was alkaline by 0.1 unit and unaffected by colicin. These results suggest that colicin K does not completely depolarize the membrane potential and does not interfere with the component of membrane energization generated by electron transport. Colicin K does not act as a cationophore. The partial depolarization of the membrane may account for the inhibition of active solute transport caused by colicin K.

The concentrating mechanism in the renal medulla

The general nature of the process that is responsible for the formation of concentrated urine is well-known and little useful purpose would be served by reviewing it here. The subject is covered by a number of articles and book chapters that have been published in recent years [1–6]. Although for some years controversy has surrounded the question of the identity of the countercurrent multiplier, particularly in the inner medulla, it is now generally accepted that the loop of Henle is indeed the countercurrent multiplier, as originally proposed by Wirz, Hargitay and Kuhn [7], and that the thin segment of the loop constitutes the multiplier in the inner medulla. Further, little question remains concerning the view that the ascending thin limb is the source of the salt that is responsible for the increase in sodium and chloride concentration from the base of the inner medulla to the tip of the papilla. The most interesting question that remains concerns the nature of the process by which salt is transferred from the lumen of the thin ascending limb to the interstitium of the medulla. This in turn relates closely to the nature of the process by which solute is concentrated in the descending thin limb of Henle's loop as fluid flows from the outer medulla to the hairpin turn. This review will be concerned primarily with the various hypotheses that have been proposed in explanation of the multiplier function of the thin segment of the loop and the experimental observations that bear upon these hypotheses. Because of questions raised on morphological grounds concerning the capacity of the thin segment to behave as a countercurrent multiplier and because the earlier observations of the behavior of this segment left in doubt whether it possessed the permeability properties and the capacity for active transport that were presumed to be necessary for the multiplier function, a number of alternative mechanisms were proposed that would have placed responsibility for the concentrating function of the inner medulla in other structures [8–10]. Theoretical considerations or experimental observations or both made it apparent that none of these alternative proposals would account for the known properties of the inner medulla. When it was shown that the fluid in the thin ascending limb has a lower osmolality than fluid in the descending limb at the same level and that the deficit in osmolality was largely accounted for by the deficit in sodium chloride concentration [11] and further that the difference was attributable to removal of solute rather than addition of water [12], it seemed clear that the thin segment is indeed the counter-current multiplier. Active transport of salt out of the thin ascending limb seemed the only reasonable possibility despite the lack of success in attempts to detect such transport [13, 14]. This thinking perhaps reflected concentration on and attempts to adapt the counter-current multiplier models proposed by Hargitay and Kuhn [15] and Kuhn and Ramel [16] which derived their function from the movement of water driven by a hydrostatic pressure gradient or the transport of solute from one limb of the multiplier to the other. In fact, in the earlier model of Kuhn and Ryffel [7], no active transport of solute or movement of water in response to a difference in hydrostatic pressure was involved. Instead, the energy for driving the counter-current multiplier had been derived from the potential energy of a concentrated solution of a second solute. is concerning this paper of Kuhn and Ryffel [7] that Wirz has appropriately said; It is questionable that this paper was thoroughly studied by many who quoted it. [4]. The principle embodied in the model of Kuhn and Ryffel is illustrated in Fig. 1. The recognition that the urine contained in the collecting ducts represents the concentrated solution of a second solute, urea, led Stephenson [18] and Kokko and Rector [19] independently and more or less simultaneously to propose models for the concentrating process in the inner medulla in which the movement of salt out of the ascending limb was facilitated by or even completely driven by favorable salt concentration gradients created by the presence of high urea concentrations in the medullary interstitium. 1

Electrical Properties and Ion Permeabilities in Intestinal Epithelia

The ionic permeabilities and conductive properties across intestinal epithelia were reviewed from the electrophysiological point of view. Based on our own data on the electrical parameters required for application of the equivalent circuit analysis, the contribution of an extracellular shunt conductance and that of an electrogenic sodium pump to the electrical properties of small intestine were estimated. In order to throw light upon the origin of a solute evoked potential changes, the changes in electrical parameters induced by an active solute transport were discussed.

Energy transduction in Escherichia coli. Genetic alteration of a membrane polypeptide of the (Ca2+,Mg2+)-ATPase.

Recent genetic analyses of the membrane components involved in energy transduction in Escherichia coli have concentrated on the (Ca2+, Mg2+)-ATPase complex (EC 3.6.1.3). Many mutants have been described with altered biochemical properties and defects in energy-requiring processes such as oxidative phosphorylation, transhydrogenase activity, and active transport of several solutes. This report describes the isolation of a mutant strain of E. coli that is defective in several energy-requiring processes. The strain BG-31 was obtained by "localized mutagenesis" using phage P1c1. The mutation maps at approximately 73.5 min on the E. coli chromosome. Reversion and suppression analyses indicate that the defect is the result of a single amber mutation. This strain is unable to utilize succinate, D-lactate, or malate for growth. Mutant cells are unable to couple the energy derived from the hydrolysis of ATP to the active transport of proline, although coupling of energy derived from electron transport to solute transport appears normal when examined in both cells and isolated membrane vesicles. Isolated membranes of the mutant are unable to couple the energy derived from the hydrolysis of ATP to transhydrogenase activity while they can utilize the energy generated from electron transport to drive transhydrogenase activity. Extracts of strain BG-31 have normal levels of (Ca2+, Mg2+)-ATPase activity. The ATPase portion of the complex, bacterial F1 (BF1), is poorly attached to the membrane portion of the complex. In vitro reconstitution of transhydrogenase activity with stripped membrane fractions and crude preparations of BF1 localize the defect in strain BG-31 to the membrane portion of the complex. Analysis of membranes of the strain BG-31 by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate demonstrate the absence of a single polypeptide of molecular weight about 54,000 and the appearance of a new polypeptide of lower molecular weight, about 25,000. Analysis of a spontaneous revertant of BG-31 shows complete restoration of the parental phenotype including the gel patterns. The characterization of this mutant provides the first demonstration of the consequences of a structural gene mutation on a polypeptide in the membrane portion of the complex and represents the initial stages in what we hope will be the biochemical definition and functional characterization of this important energy-transducing system.

Simultaneous Uptake of Water and Solutes by Plant Roots1

AbstractA theory describing the hydraulic and osmotic transport of water and the diffuse, convective and active transport of solutes across root membranes is formulated. The theory predicts the dependence of the ratio of the osmotic pressures of the nutrient and xylem solutions and of the solute flux upon the rate of water uptake. The theory also predicts a nonlinear relationship between the flux of water and the pressure difference across root membranes. The results are shown to be in good qualitative agreement with a variety of observations on simultaneous uptake of water and solutes.

Effects of ouabain on the function and structure of a cell line (MDCK) derived from canine kidney. I. Light microscopic observations of monolayer growth.

MDCK is a transformed cell line derived from normal dog kidney. It exhibits qualities of renal tubular epithelium and of papillary adenocarcinoma. On solid substrates, MDCK forms confluent monolayers that are studded with multicellular blisters and cordlike structures. Ouabain, at a concentration of 4×10−8 m, abolishes blister formation within 24 hr; withdrawal of the drug brings about reappearance of the blisters. Ouabain-sensitive ATPase activity has been demonstrated in these cells by biochemical measurement. These findings suggest that blister formation in MDCK monolayer growth is associated with active transport of solutes accompanied by water and that 4×10−8 m of ouabain interferes with these transport systems. As an additional early effect, the drug decreases the frequency of mitosis. The exposure of MDCK monolayers to ouabain for several weeks results in profound cytological alterations. A marked eosinophilic stippling of the periphery of chronically exposed cells is seen with the light microscope. After prolonged exposure to ouabain, the cell population of MDCK monolayers becomes clearly heterogeneous, with frequent giant cells and foci of small, hyperchromatic proliferating cells. The small cells may indicate the appearance of ouabain-resistant strains.

Criterion for active fluid secretion in vivo.

THE question routinely arises as to whether a given fluid secretion process is active, in the sense that the driving force is created by the epithelial cells at the expense of metabolic energy, or passive, that is, with the epithelium acting simply as a resistance to externally provided driving forces. This definition of active transport includes water transfer secondary to active solute transport. The purpose of this communication is to suggest a simple experimental in vivo procedure which can provide strong evidence that the process is active, and to describe examples of its application to the study of three types of intestinal secretion.

Critique of current theories of corneal hydration control

The abilities of several current theories of corneal hydration control to explain some aspects of in vivo corneal behavior are examined. The theories are those based on active endothelial transport of water, solute or isotonic solution from the stroma to the anterior chamber, and a theory in which no such pump is postulated but which relies heavily on the unsteady character of corneal dynamics to explain how the normal corneal thickness is attained. The corneal phenomena to be explained are selected because they differentiate among the theories and include the effects of artificial endothelia and epithelia, and of changes in tear tonicity. None of the hydration control theories definitively explain all the corneal responses examined. It is concluded that (i) transepithelial water flow and corneal unsteadiness are essential features of any realistic description of corneal behavior; (ii) additional computational capability must be developed before the theory which contains these features can be completely evaluated; and (iii) a synthesis of these theories, in which a fundamentally unsteady cornea possesses an endothelial pump, is not unreasonable.

Corneal hydration and metabolically dependent transcellular passive transfer of water

A theoretical model of the fluid pump in the corneal endothelium of the rabbit is presented. It is proposed that the stromal and aqueous surfaces of the endothelial cells have different solute reflection coefficients and that an adequate solute concentration is maintained in the cells by a mechanism dependent on metabolic energy. The model does not require transendothelial active transport of either solute or water. However, it requires the net volume flow observed through the isolated endothelium from stroma to aqueous to occur across the cells. Two situations are possible: (1) that the osmolarity of the cells is lower than the aqueous solution in conjunction with the aqueous side of the cells having the larger reflection coefficient; (2) that the osmolarity of the cells is higher than that in the stromal solution in conjunction with the stromal side of the cells having the higher reflection coefficient. A consequence of these requirements is that in case 1 the hydrostatic pressure within the endothelial cell must be less than the hydrostatic pressure in the stromal solution. In case 2 the intracellular hydrostatic pressure must be greater than the hydrostatic pressure of the aqueous solution. In vivo when the eye is closed there is zero net volume flow across the endothelium. There will be an anteriorly directed volume flow through the intercellular channels equal in magnitude to the posteriorly directed flow across the cells. This will produce a circulation of volume flow across the endothelium. When the eye is opened evaporation will take place across the epithelium, resulting in a net volume flow from the aqueous fluid into the stromal fluid. While the volume flow through the intercellular channels should remain anteriorly directed, the volume flow across the endothelial cells may be either anteriorly or posteriorly directed, depending on the values of pressures, concentrations and reflection coefficients. Two independent theoretical estimates of the net volume flow across the isolated endothelium can be made and compared with experimental results. These estimates are 3·35 μl/hr/cm 2 and 2·56 μl/hr/cm 2. They are in good agreement with the average experimental value of 6·5 μl/hr/cm 2 (Maurice, 1972).

Ultrastructure of the sexual segments of the kidney in male and female lizards, Cnemidophorus l. lemniscatus (L.).

Kidneys of adult male and female lizards were studied by electron microscopy, in order to understand the ultrastructure of the collecting duct and a differentiated part thereof, the sexual segment, which is an important accessory sexual organ. First portion of sexual segment in males: The cells are filled with large secretory granules of a wide range of opacities. The granular endoplasmic reticulum is abundant; basal formations of superimposed flat cisternae are frequent. Distended vesicles and microvesicles prevail in the supranuclear, well developed Golgi apparatus. Evidences indicate that secretion of these cells is holocrine. Second portion of sexual segment in males: All of the secretory granules are apical in location and relatively electron-opaque; they show a denser core. This core is formed by a substance which, after lying in contact with ribosomes, enters the secretory vesicles of the highly developed Golgi apparatus. A lighter substance is then condensed around it. The secretion of the granules is merocrine. The granular endoplasmic reticulum is very abundant in these cells, but basal ergastoplasmic formations are lacking. Sexual segment in females: The cells show features similar to those of the male first portion, but they are smaller. Undifferentiated collecting duct: Most of the cells are mucigenic. They have small ovoid, apical secretory granules. The density of the granules varies from cell to cell; when they are electron-lucent, they exhibit laminar or dotted opaque figures. Moderately developed Golgi apparatus and granular endoplasmic reticulum, as well as elongated mitochondria, occur in mucigenic cells. Intercalated among the latter are non-secretory cells. They have very abundant mitochondria, numerous microvilli, many pinocytic and smooth-membrane vesicles, whereas the organelles participating in synthetic processes are poorly developed; their function is most likely related to active solute transport.

The role of secretion and pressure-dependent flow in aqueous humor formation

The role of the capillary filtration pressure and secretory activity in determining the rate of net inward movement of solute and water across the ciliary processes is examined theoretically using previously published experimental data. The theoretical approach, based on a dimensionless diffusion model ( Weinbaum and Goldgraben, 1972) has yielded results which are in close agreement with experimental data for both living and dead eyes. It is concluded that the formation of the aqueous humor is a pressure dependent mechanism associated with an active transport of solute; the latter being responsible for 30–40% of the total flow. In keeping with present concepts of solute-water coupled flow in epithelial systems it is assumed that the solute is actively transported into the extracellular channels of the ciliary epithelium from the adjacent cells and that the water movement is passive.

Water-solute coupling and ion selectivity in epithelia.

Water transport across epithelia results from local osmotic gradients set up within the epithelium by active solute transport. These gradients arise in long, narrow, dead-end channels, which function as standing-gradient flow systems. Mathematical analysis of a simple model of such a flow system suggests that the ultrastructural geometry of epithelia accounts for the principal features of water-to-solute coupling. ‘Backwards’ channels are expected to differ from ‘forwards’ channels in being hypotonic rather than hypertonic, in their capacity for osmotic filtration, and in being restricted to the active transport of major plasma constituents. Epithelial pumps and other biological systems distinguish remarkably between closely similar ions, such as Na + and K + , Cl - and I - , and Ca 2+ and Mg 2+ . Qualitative regularities in discrimination, the so-called selectivity sequences, and quantitative regularities, the so-called selectivity isotherms, make it possible to predict the potencies of untested ions in a given biological system, once the relative effects of two related ions are known for that system. The observed selectivity sequences for the principal inorganic ions of biological interest have been correctly reconstructed by comparing the ions’ hydration energies with their interaction energies with membrane sites of different strengths. Details of the selectivity isotherms may provide information about the molecular structure of the biological sites.

A discussion on active transport of salts and water in living tissues. Introductory remarks.

It is a generally accepted viewpoint that the processes underlying active transport in tissues are basically the same as those which are operative in individual cells. However, the organization of cells to form epithelia seems to endow them with new potentialities with respect to apparently active transport of solutes and water not usually recognized in individual cells. The new potentialities probably can be traced back to two main sources: (1) that the cells in an epithelium are polarized so that the ‘inward’ and ‘outward’ facing membranes have different properties, and (2) the presence of a system of interspaces which is usually more or less closed towards one side of the epithelium and more open toward the other. In principle the interspace system allows relatively rapid bulk flow which in turn may give rise to ‘solvent drag’, ‘anomalous solvent drag’, and in specialized structures even to counter-current interactions between different streams.

A sodium-dependent sugar co-transport system in bacteria

Summary A characteristics difference between active transport systems in bacterial and animal cells is that the latter usually require sodium ions and operate by the process of co-transport. The melibiose permease system (TMG permease II) of Salmonella typhimurium has now been identified as a sodium-dependent co-transport system. Co-transport, and the analogous mechanism, counter-transport, may be the underlying mechanisms for the active transport of many solutes by bacterial cells, although they may be difficult to detect.

Ion transport in rabbit ileal mucosa. I. Na and Cl fluxes and short-circuit current.

Ion transport in rabbit ileal mucosa. I. Na and Cl fluxes and short-circuit current.

Standing-gradient flows driven by active solute transport

This paper shows that a relatively simple analytic treatment preserves the main features of the equations governing coupled solute and water flow in a long channel closed at one end. Until now, these equations have only been treated numerically. Among the new conclusions yielded by the present study of the standing gradient model are that (i) fluid transport depends on the product of tube radius and solute diffusion constant, (ii) the channel cross-section influences flow only through its perimeter to area ratio, (iii) flow depends only weakly on solute transport site, (iv) the observed weak dependence of transported osmolarity on transport rate is to be expected.

Osmotic swelling of intestinal epithelial cells during active sugar transport.

ARTICLESOsmotic swelling of intestinal epithelial cells during active sugar transportTZ Csaky, and G EspositoTZ Csaky, and G EspositoPublished Online:01 Sep 1969https://doi.org/10.1152/ajplegacy.1969.217.3.753MoreSectionsPDF (753 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByChapter 1 The role of volume regulation in intestinal transport: Insights from villus cells in suspensionVolume Regulation in Transporting EpitheliaBiology Of Sodium‐Absorbing Epithelial Cells: Dawning of a New Era1 January 2011Dietary Carbohydrate and the Kinetics of Intestinal Functions in Relation to Hexose AbsorptionNa+ and K+ fluxes stimulated by Na+-coupled glucose transport: Evidence for a Ba2+-insensitive K+ efflux pathway in rabbit proximal tubulesThe Journal of Membrane Biology, Vol. 105, No. 3Electrophysiological Studies of Sodium Cotransport in Epithelia: Toward a Cellular ModelAnnals of the New York Academy of Sciences, Vol. 456, No. 1 Membrane TranSodium-Coupled Sugar Transport: Effects on Intracellular Sodium Activities and Sodium-Pump ActivityScience, Vol. 224, No. 4654Basolateral Membrane Properties of Sodium-absorbing EpitheliaIntestinal Permeability of Water-Soluble Nonelectrolytes: Sugars, Amino Acids, PeptidesTransapical Na+ electrochemical potential difference and solute accumulation in Aplysia californica enterocytesComparative Biochemistry and Physiology Part A: Physiology, Vol. 78, No. 1Effect of Galactose on Intracellular Potential and Sodium Activity in Urodele Small Intestine. Evidence for Basolateral Electrogenic TransportTransport Across Small IntestineEffects of glucose and ouabain on transepithelial electrical resistance and cell volume in stripped and unstripped goldfish intestinePfl�gers Archiv European Journal of Physiology, Vol. 383, No. 1Solute Transport Process in Intestinal Epithelial Cells9 July 2009 | Membrane Biochemistry, Vol. 2, No. 3-4Glucose transport by rat small intestine after extensive small-bowel resectionThe American Journal of Digestive Diseases, Vol. 23, No. 6Experimental Studies on Fluid Pathophysiology in Small Intestinal Obstruction in the Rat23 February 2010 | Scandinavian Journal of Gastroenterology, Vol. 13, No. 3Electrical properties and active solute transport in rat small intestine26 July 2013 | The Journal of Membrane Biology, Vol. 31, No. 1Extracellular space values and intracellular ionic concentrations in the isolated midgut of Philosamia cynthia and Bombyx moriExperientia, Vol. 33, No. 8Water absorption and swelling in the rat small intestine in vitroPfl�gers Archiv European Journal of Physiology, Vol. 369, No. 1Intracellular cationic pattern along the intestine of Rana esculentaComparative Biochemistry and Physiology Part A: Physiology, Vol. 58, No. 3IONIC ACTIVITIES AND SOLUTE TRANSFER IN EPITHELIAL CELLS OF THE SMALL INTESTINEEffect on ethyl acetate on the transport of sodium and glucose in the hamster small intestine in vitroBiochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 426, No. 3Bioelectric Parameters and Sodium Transport in Bullfrog Small IntestineThe electrophysiological characteristics of glucose absorption of the goldfish intestine as compared to mammalian intestinesComparative Biochemistry and Physiology Part A: Physiology, Vol. 54, No. 1The Present State of the Carrier HypothesisEffect of K+ and K+ gradients on accumulation of sugars by isolated intestinal epithelial cellsThe Journal of Membrane Biology, Vol. 12, No. 1Interaction between Na+-dependent transport systems for sugars and amino acids. Evidence against a role for the sodium gradientThe Journal of Membrane Biology, Vol. 12, No. 1Coupling between Na+ and sugar transport in small intestineBiochimica et Biophysica Acta (BBA) - Reviews on Biomembranes, Vol. 300, No. 1Activities of Sodium and Potassium Ions in Epithelial Cells of Small IntestineScience, Vol. 175, No. 4027The extracellular space of rat intestine ?in vivo?Pfl�gers Archiv European Journal of Physiology, Vol. 331, No. 1Transport of Carbohydrates by Animal CellsDrug Transport III: Influence of Various Sugars on Passive Transfer of Several Drugs Across the Everted Rat IntestineJournal of Pharmaceutical Sciences, Vol. 60, No. 2Passive sugar flux across frog jejunum in vitroPfl�gers Archiv European Journal of Physiology, Vol. 328, No. 1Studies on intestinal fluid transport I. Estimation of the extracellular space of everted sacs of rat small intestineBiochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 211, No. 3Studies on intestinal fluid transport II. The location of fluid accumulated in the wall of rat jejunum during incubation in vitroBiochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 211, No. 3 More from this issue > Volume 217Issue 3September 1969Pages 753-755 Copyright & PermissionsCopyright © 1969 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1969.217.3.753PubMed5807697History Published online 1 September 1969 Published in print 1 September 1969 Metrics

Role of sodium in the intestinal active transport of organic solutes.

IT is well established that the active transport of hexoses and amino-acids in the intestine is dependent on sodium. To account for this, Crane1 suggested a coupling between sodium and hexose transfer and this idea was developed further by Schultz and Zalusky2, who considered that an electrogenic sodium pump was the fundamental process which made energy available for transfer of other substances.