A comment on: 'effect of starvation on glucose transport and membrane fluidity in rat intestinal epithelial cells', by: P.D. Gupta and A.A. Wahead (FEBS Letters, 300: 263-267).
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Animals↗
Biomedical subjects
H Murer
Publications and source records attributed to H Murer.
Poly(A)+ RNA from rabbit intestinal mucosa induces b0,+ and y+ amino acid transport activities in Xenopus laevis oocytes.
Injection of poly(A)+ RNA (mRNA) isolated from rabbit intestinal mucosa into Xenopus laevis oocytes results in an increase in sodium-independent uptake of L-[3H]leucine, L-[35S]cystine, and L-[3H]arginine. This uptake activity is related to an mRNA species corresponding to the recently isolated rabbit kidney cortex cDNA clone rBAT (related to b0,+ amino acid transporter; Bertran, J., Werner, A., Stange, G., Markovich, D., Moore, M. L., Biber, J., Testar, X., Zorzano, A., Palacin, M., and Murer, H. (1992) Proc. Natl. Acad. Sci. U.S.A. 281, 717-723) and to a protein involved in amino acid transport via system y+. This conclusion is based on the following observations: 1) mRNA isolated from mucosa of duodenum, jejunum, and ileum, but not from colon, induces sodium-independent uptake of L-leucine, L-cystine, and L-arginine. 2) In Northern blot analysis, mRNA isolated from mucosa of duodenum, jejunum, and ileum, but not from colon, hybridizes to an rBAT cDNA probe, with signals of 2.2-2.3 kilobases and 3.7-3.9 kilobases. 3) mRNA isolated from mucosa of jejunum induces sodium-independent uptake of L-leucine and L-cysteine which shows an inhibition pattern corresponding to system b0,+; the inhibition pattern of mRNA-induced uptake of L-arginine is compatible with the contribution of system b0,+ and y+. 4) Hybrid depletion with an rBAT antisense oligonucleotide greatly prevents the mRNA-dependent induction of uptake of L-cystine (greater than 90%) and of L-leucine (approximately 75%); it reduces to about 50% the induction of L-arginine uptake. 5) After separation of mRNA on a sucrose density gradient, the fractions resulting in expression of b0,+ transport activity were also those hybridizing with rBAT cDNA; induction of transport activity from these fractions was also sensitive to hybrid depletion. 6) The mRNA-induced component of L-arginine uptake which is resistant to rBAT hybrid depletion is inhibited by L-homoserine, only in the presence of sodium; thus, it is related to a system y(+)-like activity.
Amino Acids↗
Expression cloning of a cDNA from rabbit kidney cortex that induces a single transport system for cystine and dibasic and neutral amino acids.
We have isolated a cDNA clone by screening a rabbit kidney cortex cDNA library for expression of sodium-independent transport of L-arginine and L-alanine in Xenopus laevis oocytes. Expressed uptake relates to a single component of sodium-independent transport for dibasic and neutral amino acids. This transport activity resembles the functionally defined system b0,+ and carries cystine and dibasic amino acids with high affinity. The rBAT (b0,+ amino acid transporter-related) mRNA is found mainly in kidney and intestinal mucosa. It encodes a predicted 77.8-kDa protein with only one putative transmembrane domain and seven potential N-glycosylation sites. This protein could either be a constitutive element or a specific activator of system b0,+.
Amino Acid Sequence↗
Stimulation of system y(+)-like amino acid transport by the heavy chain of human 4F2 surface antigen in Xenopus laevis oocytes.
A kidney cortex cDNA clone (rBAT) has recently been isolated, which upon in vitro transcription and capping complementary RNA (cRNA) and injection into Xenopus laevis oocytes induces a system b0,(+)-like amino acid transport activity. This cDNA encodes a type II membrane glycoprotein that shows significant homology to another type II membrane glycoprotein, the heavy chain of the human and mouse 4F2 surface antigen (4F2hc). Here we demonstrate that injection of human 4F2hc cRNA into oocytes results in the activation of a cation-preferring amino acid transport system that appears to be identical to the y(+)-like transport already present in the oocyte. This is based on the following results: (i) Injection of in vitro transcripts from 4F2hc cDNA (4F2hc cRNA) into oocytes stimulates up to 10-fold the sodium-independent uptake of L-arginine and up to 4.1-fold the sodium-dependent uptake of L-leucine. In contrast, 4F2hc cRNA does not increase the basal sodium-independent uptake of L-leucine. (ii) Basal and 4F2hc cRNA-stimulated sodium-independent uptake of L-arginine is completely inhibited by L-leucine in the presence of sodium. Similarly, the basal and 4F2hc cRNA-stimulated sodium-dependent uptake of L-leucine is entirely inhibited by L-arginine. (iii) The stimulation of sodium-independent uptake of L-arginine and the stimulation of sodium-dependent uptake of L-leucine induced by injection of 4F2hc cRNA are both completely inhibited by dibasic L amino acids and to a lesser extent by D-ornithine. (iv) Both basal and 4F2hc cRNA-stimulated sodium-independent uptake of L-arginine show two additional characteristics of the system y+ transport activity: inhibition of L-arginine uptake by L-homoserine only in the presence of sodium and an increase in the inhibition exerted by L-histidine as the extracellular pH decreased. Our results allow us to propose that an additional family of type II membrane glycoproteins (composed by rBAT and 4F2hc) is involved in amino acid transport, either as specific activators or as components of amino acid transport systems.
Amino Acid Sequence↗
Expression of Na(+)-independent amino acid transport in Xenopus laevis oocytes by injection of rabbit kidney cortex mRNA.
Poly(A)+ mRNA was isolated from rabbit kidney cortex and injected into Xenopus laevis oocytes. Injection of mRNA resulted in a time- and dose-dependent increase in Na(+)-independent uptake of L-[3H]alanine and L-[3H]arginine. L-Alanine uptake was stimulated about 3-fold and L-arginine uptake was stimulated about 8-fold after injection of mRNA (25-50 ng, after 3-6 days) as compared with water-injected oocytes. T.I.C. of oocyte extracts suggested that the increased uptake actually represented an increase in the oocyte content of labelled L-alanine and L-arginine. The expressed L-alanine uptake, obtained by subtracting the uptake in water-injected oocytes from that in mRNA-injected oocytes, showed saturability and was inhibited completely by 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) and L-arginine. The expressed L-arginine uptake in mRNA-injected oocytes also showed saturability, being completely inhibited by L-dibasic amino acids) and partially inhibited by BCH. Expression of both L-alanine and L-arginine uptake showed clear cis-inhibition by cationic (e.g. L-arginine) and neutral (e.g. L-leucine) amino acids. In all, this points to the expression of a Na(+)-independent transport system with broad specificity (i.e. b degree, (+)-like). In addition, part of the expressed uptake of L-arginine could be due to a system y(+)-like transporter. After size fractionation through a sucrose density gradient, the mRNA species encoding these increased transport activities (Na(+)-independent transport of L-alanine and of L-arginine) were found in fractions of an average mRNA chain-length of 1.8-2.4 kb. On the basis of these results, we conclude that Na(+)-independent transport system(s) for L-alanine and L-arginine from rabbit renal cortical tissues, most likely proximal tubules, are expressed in Xenopus laevis oocytes. These observations may represent the first steps towards expression and cloning of these transport pathways.
Alanine↗
Na+/H(+)-exchange in A6 cells: polarity and vasopressin regulation.
We have analyzed the mechanism of Na(+)-dependent pHi recovery from an acid load in A6 cells (an amphibian distal nephron cell line) by using the intracellular pH indicator 2'7'-bis(2-carboxyethyl)5,6 carboxyfluorescein (BCECF) and single cell microspectrofluorometry. A6 cells were found to express Na+/H(+)-exchange activity only on the basolateral membrane: Na+/H(+)-exchange activity follows simple saturation kinetics with an apparent Km for Na+ of approximately 11 mM; it is inhibited in a competitive manner by ethylisopropylamiloride (EIPA). This Na+/H(+)-exchange activity is inhibited by pharmacological activation of protein kinase A (PKA) as well as of protein kinase C (PKC). Addition of arginine vasopressin (AVP) either at low (subnanomolar) or at high (micromolar) concentrations inhibits Na+/H(+)-exchange activity; AVP stimulates IP3 production at low concentrations, whereas much higher concentrations are required to stimulate cAMP formation. These findings suggest that in A6 cells (i) Na+/H(+)-exchange is located in the basolateral membrane and (ii) PKC activation (heralded by IP3 turnover) is likely to be the mediator of AVP action at low AVP concentrations.
Amiloride↗
H+ extrusion by an apical vacuolar-type H(+)-ATPase in rat renal proximal tubules.
The activity of Na+/H(+)-exchange and H(+)-ATPase was measured in the absence of CO2/HCO3 by microfluorometry at the single cell level in rat proximal tubules (superficial S1/S2 segments) loaded with BCECF [2'7'-bis(carboxyethyl)5-6-carboxyfluorescein- acetoxymethylester]. Intracellular pH (pHi) was lowered by a NH4Cl-prepulse technique. In the absence of Na+ in the superfusion solutions, pHi recovered from the acid load by a mechanism inhibited by 0.1 microM bafilomycin A1, a specific inhibitor of a vacuolar-type H(+)-ATPase. Readdition of Na+ in the presence of bafilomycin A1 produced an immediate recovery of pHi by a mechanism sensitive to the addition of 10 microM EIPA (ethylisopropylamiloride), a specific inhibitor of Na+/H+ exchange. The transport rate of the H(+)-ATPase is about 40% of Na+/H(+)-exchange activity at a similar pHi (0.218 +/- 0.028 vs. 0.507 +/- 0.056 pH unit/min. Pre-exposure of the tubules to 30 mM fructose, 0.5 mM iodoacetate and 1 mM KCN (to deplete intracellular ATP) prevented a pHi recovery in Na(+)-free media; readdition of Na+ led to an immediate pHi recovery. Tubules pre-exposed to Cl(-)-free media for 2 hr also reduced the rate of Na(+)-independent pHi recovery. In free-flow electrophoretic separations of brush border membranes and basolateral membranes, a bafilomycin A1-sensitive ATPase activity was found to be associated with the brush border membrane fraction; half maximal inhibition is at 6 x 10(-10) M bafilomycin A1.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine Triphosphate↗
Apical and basolateral Na/H exchange in cultured murine proximal tubule cells (MCT): effect of parathyroid hormone (PTH).
Kidney proximal tubule Na/H exchange is inhibited by PTH. To analyze further the cellular mechanisms involved in this regulation we have used MCT cells (a culture of SV-40 immortalized mouse cortical tubule cells) grown on permeant filter supports. Na/H exchange was measured using single cell fluorescence microscopy (BCECF) and phosphate transport (measured for comparisons) by tracer techniques. MCT cells express apical and basolateral Na/H exchangers which respond differently to inhibition by ethylisopropylamiloride and by dimethylamiloride, the basolateral membrane transporter being more sensitive. Apical membrane Na/H exchange was inhibited by PTH (10(-8) M; by an average of 25%); similar degrees of inhibition were observed when cells were exposed either to forskolin, 8-bromo-cAMP or phorbol ester. Basolateral membrane Na/H exchange was stimulated either by incubation with PTH (to 129% above control levels) or by addition of phorbol ester (to 120% above control levels); it was inhibited after exposure to either forskolin or 8-bromo-cAMP. The above effects of PTH and phorbol ester (apical and basolateral) were prevented by preincubation of cells with protein kinase C antagonists, staurosporine and calphostin C; both compounds did not affect forskolin or 8-bromo-cAMP induced effects. PTH also inhibited apical Na-dependent phosphate influx (29% inhibition at 10(-8) M); it had no effect on basolateral phosphate fluxes (Na-dependent and Na-independent). Incubation with PTH (10(-8) M) resulted in a rapid and transient increase in [Ca2+]i (measured with the fluorescent indicator, fura-2), due to stimulation of a Ca2+ release from intracellular stores. Exposure of MCT cells to PTH did not elevate cellular levels of cAMP. Taken together, these results suggest that PTH utilizes in MCT cells the phospholipase C/protein kinase C pathway to differently control Na/H exchangers (apical vs. basolateral) and to inhibit apical Na/Pi cotransport.
Alkaloids↗
Characterization of basolateral Na/H exchange (Na/H-1) in MDCK cells.
MDCK cells were grown to confluent monolayers on permeant filter supports; pH was analysed by using the pH-sensitive fluorescent probe 2'7'-biscarboxyethyl-5,6-carboxyfluorescein and a routine spectrofluorometer equipped with a perfusion cuvette [Krayer-Pawlowska et al. (1990) J Membr Biol 120:173-183]. Superfusion of the basolateral (but not apical) cell surface with Na(+)-containing solutions led to immediate recovery of pHi from an acid load (NH4 prepulse). This pHi recovery was reversibly inhibited by ethylisopropylamiloride indicating Na/H exchange activity. Na/H exchange activity showed an apparent Km for Na+ of about 25 nM Na+ and an apparent Ki for inhibition by dimethylamiloride of around 0.2 microM; inhibition by dimethylamiloride was competitive with Na+ interaction. Lowering pHi prior to analysis of Na/H exchange leads to sharp activation of Na/H exchange; the apparent Vmax for Na/H exchange is increased more than tenfold by lowering the pHi from 7.0 to 6.7 without an effect on apparent Km values for Na+ interaction. It is concluded that MDCK cells (strain I) grown on a permeant support contain only basolateral Na/H exchange activity, most likely Na/H-1 [for nomenclature see Igarashi et al. (1991) Kidney Int 40:S84-S89].
Amiloride↗
Polarized expression of Na+/H+ exchange activity in LLC-PK1/PKE20 cells: II. Hormonal regulation.
LLC-PK1/PKE20 cells (a continuous epithelial cell line) has two different Na/H exchange activities: Na/H-1 located in the basolateral membrane and Na/H-2 located in the apical membrane [Casavola et al. (1989) Biochem Biophys Res Commun 165:833-837; Haggerty et al. (1988) Proc Natl Acad Sci USA 86:6797-6801]. In the present report we have studied hormone regulation of these exchange activities by measuring Na-dependent recovery of pHi from an acid load (by using microspectrofluorometry and 2,7-bis(carboxyethyl)-5,6-carboxyfluorescein) in response to activation of regulatory cascades by either pharmacological agents or by vasopressin or calcitonin. Agents leading to activation of protein kinase A (cAMP-dependent), such as forskolin (10 microM), 8-Br-cAMP (0.25 mM), and isobutylmethylxanthine (0.5 mM), inhibited Na/H-2 and Na/H-1 by an average of 49%. Stimulation of protein kinase C by a phorbol ester (phorbol 12-myristate 13-acetate, TPA, 100 nM) inhibited Na/H-2 (by an average of 48%) and stimulated Na/H-1 (by an average of 38%); these effects of TPA were also observed in the presence of forskolin (100 microM). Addition of either vasopressin (2 microM) or calcitonin (0.3 microM) onto both sides of the monolayer decreased the activity of Na/H-2 by an average of 26.3% and 27.7% respectively, and stimulated the activity of Na/H-1 by an average of 17.4% and 38.7% respectively; exposure of cells to either hormone stimulated production of cAMP and inositol trisphosphate, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenylyl Cyclases↗
Influence of extracellular pH and perfusion rate on Na+/H+ exchange in cultured opossum kidney cells.
Studies were undertaken in cultured opossum kidney (OK) cells to determine whether the rate of H+ secretion by apical membrane Na+/H+ exchange is modulated by changes in extracellular pH or perfusion rate. H+ secretion was assessed in single cells by measuring the rate of Na(+)-dependent intracellular pH recovery after NH4Cl loading, using the pH-sensitive fluorescent dye, 2'7'-bis(carboxyethyl)-5,6-carboxyfluorescein, in monolayers mounted to allow independent perfusion of the apical and basolateral surfaces. At constant intracellular pH, Na(+)-dependent H+ secretion was found to be inversely related to extracellular H+ activity, and directly related to the perfusate flow rate. Inhibition of H+ secretion by perfusate acidity occurred immediately and was greater when perfusate Na+ was reduced, consistent with H+ competition with Na+ for binding to the transporter. By contrast, the effect of the perfusion rate was a delayed response, requiring 20 min of exposure, and was independent of perfusate Na+ concentration. The results indicate that both extracellular pH and the perfusion rate modulate H+ secretion by OK cells, and that the two effects are independent.
Animals↗
Effect of rabbit duodenal mRNA on phosphate transport in Xenopus laevis oocytes: dependence on 1,25-dihydroxy-vitamin-D3.
Expression of Na(+)-dependent transport of phosphate (Pi) was analysed in Xenopus laevis oocytes after injection of poly(A)-rich RNA isolated from the duodenal mucosa of rabbits with increased levels of 1,25-(OH)2-VitD3 (injection of vitamin D3 or low-Pi diet) or from control animals. In parallel, the effect of elevated levels of vitamin D3 was studied in isolated duodenal brush-border membrane vesicles. In brush-border membrane vesicles, the rate of Na(+)-Pi cotransport was found to be doubled after 1,25-(OH)2-VitD3 injections while Na(+)-D-glucose cotransport (measured as a control) was not altered. In X. laevis oocytes, Na(+)-dependent Pi uptake was increased after injection of poly(A)-rich RNA isolated from duodenal mucosa of animals with increased levels of 1,25-(OH)2-VitD3 but not after injection of poly(A)-rich RNA isolated from control animals; between the two groups of mRNA no difference in the expression of the Na(+)-D-glucose transport system was observed. Sucrose density gradient fractionation suggests that mRNA species related to the increased Na(+)-dependent Pi uptake are of average chain lengths between 2 x 10(3) and 3 x 10(3) bases (2-3 kb). It is concluded that in duodenal enterocytes 1,25-(OH)2-VitD3 increases the content of mRNA species of 2-3 kb that might be involved either directly in Na-Pi cotransport or at least in controlling its activity.
Animals↗
Aldosterone actions on basolateral Na+/H+ exchange in Madin-Darby canine kidney cells.
In recent studies, there has been a re-evaluation of the polarity of Na+/H+ exchange in Madin-Darby canine kidney (MDCK) cells. This study was designed to examine aldosterone actions on basolaterally located Na+/H+ exchange of MDCK cell monolayers grown on permeant filter supports; pHi was analysed in the absence of bicarbonate by using the pH-sensitive fluorescent probe 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein. Pre-exposure of MDCK cells to aldosterone led within 10-20 min to an alkalization of pHi (approximately 0.3 pH unit); this effect is prevented by an addition of dimethylamiloride to the basolateral superfusate. Addition of aldosterone led to stimulation of the basolaterally located Na+/H+ exchange activity (Na(+)-dependent recovery from an acid load); this effect required preincubation (more then 3 min) and was observed at 0.1 nM aldosterone. Pre-exposure (15 min) of MDCK monolayers to phorbol 12-myristate 13-acetate also led to an activation of Na+/H+ exchange; pre-exposure to 8-bromo-cAMP led to inhibition of Na+/H+ exchange activity. An inhibitory effect of aldosterone was observed if Na+/H+ exchange activity was analysed in the presence of aldosterone; the highest inhibitory effects (20%-30%) occurred at concentrations of 5 nM and higher. Aldosterone-dependent inhibition does not require preincubation and is fully reversible; it was only observed at low (20 mM) but not at high Na+ concentrations (130 mM). The data suggest that aldosterone has an instantaneous inhibitory effect on basolaterally located Na+/H+ exchange activity under conditions of low Na+, but stimulates the rate of transport activity upon preincubation under conditions of physiological Na+ concentrations.
Aldosterone↗
Transport of L-leucine hydroxy analogue and L-lactate in human small intestinal brush border membrane vesicles.
Nitrogen load can be reduced by substituting dietary protein intake with keto or hydroxy analogues of amino acids. To investigate their intestinal absorption, human jejunal brush border membrane vesicles were used to measure uptake of L-leucine hydroxy analogue (L-LHA) and L-lactate. Uptake assays were performed under voltage-clamped conditions in the presence of valinomycin and K+ inside and outside. Both inward directed H(+)- and Na(+)-gradients stimulated uptake of both substrates. The H(+)-gradient was the major driving force and led to an increased rate of L-LHA or L-lactate transport. The proton ionophore FCCP abolished the H(+)-gradient-driven but not the Na(+)-gradient-driven uptakes of both substrates. The H(+)-gradient-driven uptake of both substrates was trans-stimulated by L-LHA, D-LHA, L-valine hydroxy analogue or L-lactate, respectively. In the presence of a Na(+)-gradient the uptake of tracer L-lactate was trans-stimulated only after preloading the vesicles with L-lactate but not by L-LHA. It can be concluded that the H(+)-gradient-driven transport of L- or D-hydroxy analogues of branched chain amino acids and L-lactate across the human intestinal brush border membrane is mediated by the same carrier.
Biological Transport, Active↗
Parathyroid hormone receptors in control of proximal tubule function.
Parathyroid hormone action on renal proximal tubule function involves phospholipase C/protein kinase C as well as adenylate cyclase/protein kinase A mediated regulatory pathways. Tissue culture experiments suggest that low concentrations of PTH affect preferentially the phospholipase C/protein kinase C pathway. In vivo, both regulatory cascades are probably involved in the regulation of proximal tubule function. It is not clear at present whether the two intracellular pathways are linked to one or two PTH receptors. A polarized distribution of PTH receptor(s) involving different second messengers appears possible in proximal tubule epithelial cells. High-affinity (Kd 10(-11)-10(-12) M) PTH receptors in the range of circulating PTH concentrations in vivo remain to be identified. Structural and functional characterization of PTH receptors as well as of the PTH-sensitive intracellular mediators and transport systems form the basis for a better understanding of PTH-dependent regulation of proximal tubule function.
Absorption↗
Involvement of C3 exotoxin-sensitive G proteins (rho/rac) in PTH signal transduction in OK cells.
Parathyroid hormone (PTH) in opossum kidney (OK) cells leads to inhibition of Na-Pi cotransport, to the generation of inositol trisphosphate (IP3) and adenosine 3',5'-cyclic monophosphate (cAMP) and to a phosphorylation of proteins present in an enriched apical membrane fraction (27, 28; for review see Ref. 23). In the present report we have identified two of these phosphoproteins with molecular weights of approximately 22,000 and approximately 24,000, respectively, as guanosine 5'-triphosphate (GTP)-binding proteins, ADP-ribosylated by the Clostridium botulinum exotoxin C3 and recognized by an anti-rho polyclonal antibody but not by pan-ras monoclonal antibody; as suggested by Western-blot analysis the content of the proteins recognized by the anti-rho antibody did not alter in the membrane fraction as a function of treatment with PTH. Transient permeabilization of OK cells using streptolysin O and including the C3 exotoxin attenuated PTH-dependent inhibition of Na-Pi cotransport at hormone concentrations higher than 10(-10) M; residual PTH-dependent inhibition is equal to that observed after pharmacological activation of protein kinase A and protein kinase C, respectively. C3 exotoxin did not alter PTH-dependent generation of cAMP but modified production of IP3; it was increased at 10(-11) M and reduced at 10(-8) M PTH, respectively. It is suggested that protein kinase A may be involved in the phosphorylation of C3 exotoxin-sensitive G proteins (rho/rac). These proteins could be involved in PTH signal transduction.
ADP Ribose Transferases↗
Homer Smith Award. Cellular mechanisms in proximal tubular Pi reabsorption: some answers and more questions.
Inorganic phosphate (Pi) is reabsorbed mainly in the proximal tubule, by a second active Na-dependent transport mechanism. Na/Pi cotransport with a stoichiometry exceeding unity mediates uphill flux across the brush border membrane; at the basolateral cell surface, two separate transport systems are involved in equilibrating Pi fluxes. The protein structure of a rabbit renal cortex Na/Pi cotransport system has been identified recently by expression cloning. The regulation of tubular Pi reabsorption involves mainly alterations in the transport rate of the brush border membrane Na/Pi cotransport system. The regulation of this transport step by either parathyroid hormone (PTH) or Pi deprivation is discussed, mostly on the basis of observations made with a tissue culture model, OK cells derived from opossum kidney. In this model, PTH may use a dual signaling cascade to inhibit apical Na/Pi cotransport (phospholipase C/protein kinase C and adenylate cyclase/protein kinase A). PTH action on Na/Pi cotransport may involve an endocytosis mechanism. For the regulation of apical Na/Pi cotransport by chronic Pi deprivation, the number of "Na/Pi cotransporter" molecules seems to be unaffected; the increased transport rate is apparently related to an "unknown" stimulating event at the membrane level (e.g., a change in the lipid microenvironment), which itself is under the control of protein synthesis/degradation. The availability of new tools (cloning of Na/Pi cotransporter(s) and of PTH receptor(s)) will allow us to enter into a new era in the study of cellular mechanisms involved in proximal tubular Pi reabsorption.
Animals↗
Parathyroid hormone receptors and intracellular mediators in control of proximal tubular function.
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Kidney Tubules, Proximal↗