Inhibition of amino acid accumulation in slices of rat kidney cortex by diamide

Amino acid excretion patterns were studied in rats 2 to 12 weeks old. In general there was a decline in amino acid excretion over this period which paralleled that reported in human infants by other workers. The decrease was most marked for certain amino acids (glycine, histidine, and arginine). These changes in excretion are not explicable in terms of changes in plasma amino acid concentrations, nor is it likely that they result from differences in filtered load. They may reflect a progressive development of transport mechanisms for some amino acids over the period studied, in which case similar changes in the concentrating ability of rat kidney cortex slices would be predicted. Other possible explanations which are less readily tested include changes in permeability of the tubular cell membranes and differences in the glomerular filtering capacity relative to the amount of tubular tissue which has developed.

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The effect of phlorizin on amino acid transport in rat-kidney-cortex slices

Biochimica et Biophysica Acta ◽

10.1016/0006-3002(63)91141-7 ◽

1963 ◽

Vol 71 ◽

pp. 676-687 ◽

Cited By ~ 21

Author(s):

Stanton Segal ◽

Alberta Blair ◽

Leon E Rosenberg

Keyword(s):

Amino Acid ◽

Amino Acid Transport ◽

Rat Kidney ◽

Kidney Cortex ◽

Acid Transport ◽

Rat Kidney Cortex ◽

Cortex Slices ◽

Kidney Cortex Slices

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Cloning and functional expression of rNBC, an electrogenic Na+- HCO 3 − cotransporter from rat kidney

AJP Renal Physiology ◽

10.1152/ajprenal.1998.274.2.f425 ◽

1998 ◽

Vol 274 (2) ◽

pp. F425-F432 ◽

Cited By ~ 66

Author(s):

Michael F. Romero ◽

Peying Fong ◽

Urs V. Berger ◽

Matthias A. Hediger ◽

Walter F. Boron

Keyword(s):

Amino Acid ◽

Rat Kidney ◽

Basolateral Membrane ◽

Functional Expression ◽

Amino Acid Identity ◽

Ambystoma Tigrinum ◽

Kidney Cortex ◽

Rat Kidney Cortex ◽

Reading Frame ◽

Major Route

We have recently cloned the renal electrogenic Na+-bicarbonate cotransporter of the salamander Ambystoma tigrinum(aNBC) (M. F. Romero, M. A. Hediger, E. L. Boulpaep, and W. F. Boron. FASEB J. 10: 89, 1996; and Nature 387: 409–413, 1997). Here we report the cloning of a mammalian homolog of aNBC, named rNBC for rat Na+-bicarbonate cotransporter. NBC constitutes the major route for[Formula: see text] reabsorption and assists in Na+ reabsorption across the basolateral membrane of the renal proximal tubule (PT). We used aNBC as a probe to screen a rat kidney cortex cDNA library in λgt10 and identified several clones. Each has an initiator Met and a large open-reading frame followed by a 3′-untranslated region of ∼500 bp. The 7.5-kb mRNA for rNBC is present in kidney, liver, lung, brain, and heart. In situ hybridization with the rNBC probe in the rat kidney revealed staining in the S2 segment of PT. rNBC encodes a protein of 1,035 amino acids, with a predicted molecular mass of 116 kDa. Its deduced amino acid sequence is 86% identical to that of aNBC. Comparison of both the aNBC and rNBC sequences to the GenBank database reveals a low level of amino acid identity (∼30%) to the AE family of Cl−/[Formula: see text]exchangers. Injection of rNBC cRNA into Xenopus oocytes leads to expression of an electrogenic Na+-[Formula: see text]cotransporter that is qualitatively similar to that of aNBC but at a much lower level. Placement of the rNBC cDNA into the context of a Xenopus expression vector produces a substantial increase in rNBC expression. Addition of 1.5% CO2/10 mM[Formula: see text] elicits a hyperpolarization of >50 mV and a rapid decrease of intracellular pH (pHi), followed by an increase in pHi. Subsequent removal of Na+ in the presence of CO2/[Formula: see text]causes a depolarization of >50 mV and a concomitant decrease of pHi. Thus rNBC is in the same newly identified family of Na+-linked[Formula: see text] transporters as is aNBC.

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A comparison of the amino acid concentrating ability of the kidney cortex of newborn and mature rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y68-027 ◽

1968 ◽

Vol 46 (2) ◽

pp. 165-169 ◽

Cited By ~ 16

Author(s):

W. A. Webber ◽

J. A. Cairns

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Cell Layer ◽

Rat Kidney ◽

The Other ◽

Kidney Cortex ◽

Acid Transport ◽

Newborn Rat ◽

Rat Kidney Cortex ◽

A Cell

It has frequently been demonstrated that there are multiple mechanisms for amino acid transport and that these function to maintain a favorable intracellular level of amino acids within cells. In some instances they also make possible the transport of amino acids from one face of a cell layer to the other. In general, developing tissues have a higher concentrating ability than mature tissues. In the kidney, however, it has been observed that the ability to reabsorb amino acids may be less effective in developing than in mature organisms. Studies were carried out to determine whether the newborn rat kidney cortex differed from mature cortex in its ability to concentrate a representative group of amino acids. In general, the patterns observed for the concentrative uptake of glycine, L-leucine, α-aminoisobutyric acid, L-aspartic acid, and L-lysine were the same. In all cases uptake was initially more rapid in the mature tissue, but the concentration ratios ultimately reached were higher in the newborn tissues. It is concluded that, as in other developing tissues, newborn rat kidney cortex has a high concentrating ability and might therefore be expected to reabsorb amino acids at least as effectively as mature cortex. However the observation that uptake is relatively slow initially suggests that although the ability to establish a gradient at equilibrium is high the capacity of the system is relatively low and this may account for the apparent low capacity of the immature kidney to reabsorb amino acids.

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