Aminoglycosides inhibit hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells

2000 ◽  
Vol 78 (8) ◽  
pp. 595-602 ◽  
Author(s):  
Hyung Sub Kang ◽  
Dirk Kerstan ◽  
Long-jun Dai ◽  
Gordon Ritchie ◽  
Gary A Quamme
Keyword(s):  
Parathyroid Hormone ◽  
Distal Tubule ◽  
Distal Convoluted Tubule ◽  
Thick Ascending Limb ◽  
Clinical Use ◽  
Cellular Mechanisms ◽  
Nephron Segment ◽  
Tubule Cells ◽  
Renal Magnesium Wasting ◽  
Camp Formation

The clinical use of aminoglycosides often leads to renal magnesium wasting and hypomagnesemia. Of the nephron segments, both the thick ascending limb of Henle's loop and the distal tubule play significant roles in renal magnesium conservation but the distal convoluted tubule exerts the final control of urinary excretion. An immortalized mouse distal convoluted tubule (MDCT) cell line has been extensively used to study the cellular mechanisms of magnesium transport in this nephron segment. Peptide hormones, such as parathyroid hormone (PTH), glucagon, calcitonin, and arginine vasopressin (AVP) stimulate Mg2+ uptake in MDCT cells that is modulated by extracellular polyvalent cations, Ca2+ and Mg2+. The present studies determined the effect of aminoglycosides on parathyroid hormone (PTH)-mediated cAMP formation and Mg2+ uptake in MDCT cells. Gentamicin, a prototypic aminoglycoside, illicited transient increases in intracellular Ca2+ from basal levels of 102 ± 13 nM to 713 ± 125 nM, suggesting a receptor-mediated response. In order to determine Mg2+ transport, MDCT cells were Mg2+-depleted by culturing in Mg2+-free media for 16 h and Mg2+ uptake was measured by microfluorescence after placing the depleted cells in 1.0 mM MgCl2. The mean rate of Mg2+ uptake, d([Mg2+]i)/dt, was 138 ± 24 nM/s in control MDCT cells. Gentamicin (50 µM) did not affect basal Mg2+ uptake (105 ± 29 nM/s), but inhibited PTH stimulated Mg2+ entry, decreasing it from 257 ± 36 nM/s to 108 ± 42 nM/s. This was associated with diminished PTH-stimulated cAMP formation, from 80 ± 2.5 to 23 ± 1 pmol/mg protein·5 min. Other aminoglycosides such as tobramycin, streptomycin, and neomycin also inhibited PTH-stimulated Mg2+ entry and cAMP formation. As these antibiotics are positively charged, the data suggest that aminoglycosides act through an extracellular polyvalent cation-sensing receptor present in distal convoluted tubule cells. We infer from these studies that aminoglycosides inhibit hormone-stimulated Mg2+ absorption in the distal convoluted tubule that may contribute to the renal magnesium wasting frequently observed with the clinical use of these antibiotics.Key words: intracellular Mg2+, Mg2+ uptake, aminoglycosides, gentamicin, tobramycin, streptomycin, neomycin, parathyroid hormone, microfluorescence, cAMP measurements.

scholarly journals Insulin stimulates Mg2+ uptake in mouse distal convoluted tubule cells

1999 ◽  
Vol 277 (6) ◽  
pp. F907-F913 ◽  
Author(s):  
Long-Jun Dai ◽  
Gordon Ritchie ◽  
Brian W. Bapty ◽  
Dirk Kerstan ◽  
Gary A. Quamme
Keyword(s):  
Kinase Inhibitor ◽  
Insulin Receptors ◽  
Distal Tubule ◽  
Fold Increase ◽  
Distal Convoluted Tubule ◽  
Maximal Response ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Camp Formation

Insulin has been shown to be a magnesium-conserving hormone acting, in part, through stimulation of magnesium absorption within the thick ascending limb. Although the distal convoluted tubule possesses the most insulin receptors, it is unclear what, if any, actions insulin has in the distal tubule. The effects of insulin were studied on immortalized mouse distal convoluted tubule (MDCT) cells by measuring cellular cAMP formation with radioimmunoassays and Mg2+ uptake with fluorescence techniques using mag-fura 2. To assess Mg2+ uptake, MDCT cells were first Mg2+ depleted to 0.22 ± 0.01 mM by culturing in Mg2+-free media for 16 h and then placed in 1.5 mM MgCl2, and the changes in intracellular Mg2+ concentration ([Mg2+]i) were measured with microfluorescence. [Mg2+]i returned to basal levels, 0.53 ± 0.02 mM, with a mean refill rate, d([Mg2+]i)/d t, of 164 ± 5 nM/s. Insulin stimulated Mg2+ entry in a concentration-dependent manner with maximal response of 214 ± 12 nM/s, which represented a 30 ± 5% increase in the mean uptake rate above control values. This was associated with a 2.5-fold increase in insulin-mediated cAMP generation (52 ± 3 pmol ⋅ mg protein−1 ⋅ 5 min−1). Genistein, a tyrosine kinase inhibitor, diminished insulin-stimulated Mg2+ uptake (169 ± 11 nM/s), but did not change insulin-mediated cAMP formation (47 ± 5 pmol ⋅ mg protein−1 ⋅ 5 min−1). PTH stimulates Mg2+ entry, in part, through increases in cAMP formation. Insulin and PTH increase Mg2+ uptake in an additive fashion. In conclusion, insulin mediates Mg2+ entry, in part, by a genistein-sensitive mechanism and by modifying hormone-responsive transport. These studies demonstrate that insulin stimulates Mg2+ uptake in MDCT cells and suggest that insulin acts in concert with other peptide and steroid hormones to control magnesium conservation in the distal convoluted tubule.

scholarly journals Mg2+/Ca2+sensing inhibits hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells

1998 ◽  
Vol 275 (3) ◽  
pp. F353-F360 ◽  
Author(s):  
Brian W. Bapty ◽  
Long-Jun Dai ◽  
Gordon Ritchie ◽  
Lucie Canaff ◽  
Geoffrey N. Hendy ◽  
...  
Keyword(s):  
Distal Convoluted Tubule ◽  
Dependent Manner ◽  
Cellular Mechanisms ◽  
Polyvalent Cation ◽  
Concentration Dependent Manner ◽  
Nephron Segment ◽  
The Mean ◽  
Free Media ◽  
Cation Sensing ◽  
Camp Formation

The distal convoluted tubule plays a significant role in renal magnesium conservation. An immortalized mouse distal convoluted tubule (MDCT) cell line has been extensively used to study the cellular mechanisms of magnesium transport in this nephron segment. MDCT cells possess an extracellular polyvalent cation-sensing mechanism responsive to Mg2+, Ca2+, and neomycin. The present studies determined the effect of Mg2+/Ca2+sensing on hormone-mediated cAMP formation and Mg2+ uptake in MDCT cells. MDCT cells were Mg2+ depleted by culturing in Mg2+-free media for 16 h, and Mg2+ uptake was measured by microfluorescence after placing the depleted cells in 1.5 mM MgCl2. The mean rate of Mg2+ uptake was 164 ± 5 nM/s in control MDCT cells. Activation of Mg2+/Ca2+sensing with neomycin did not affect basal Mg2+ uptake (155 ± 5 nM/s). We have previously reported that treatment of MDCT cells with either glucagon or arginine vasopressin (AVP) stimulated Mg2+ entry. In the present studies, the addition of extracellular Mg2+ or Ca2+ inhibited glucagon- and AVP-stimulated cAMP formation and Mg2+ uptake in concentration-dependent manner with half-maximal concentrations of ∼1.5 and 3.0 mM, respectively. Exogenous cAMP or forskolin stimulated Mg2+ uptake in the presence of Mg2+/Ca2+sensing activation. We infer from these studies that Mg2+/Ca2+-sensing mechanisms located in the distal convoluted tubule may play a role in control of distal magnesium absorption.

Acid-base changes alter Mg2+ uptake in mouse distal convoluted tubule cells

1997 ◽  
Vol 272 (6) ◽  
pp. F759-F766 ◽  
Author(s):  
L. J. Dai ◽  
P. A. Friedman ◽  
G. A. Quamme
Keyword(s):  
Distal Tubule ◽  
Distal Convoluted Tubule ◽  
Membrane Voltage ◽  
Alkaline Ph ◽  
Acid Base ◽  
Cellular Mechanisms ◽  
Buffer Solution ◽  
Membrane Hyperpolarization ◽  
Ph Values ◽  
Tubule Cells

Metabolic alkalosis leads to renal magnesium conservation, whereas metabolic acidosis is associated with urinary magnesium wasting. Micropuncture studies suggest that these actions affect magnesium transport in the distal tubule. The cellular mechanisms of acid-base changes were investigated in an immortalized mouse distal convoluted tubule (MDCT) cell line. Intracellular free Mg2+ concentration ([Mg2+]i) was determined by microfluorescence using the Mg(2+)-responsive dye, mag-fura 2. Mg2+ transport was assessed as a function of change in [Mg2+]i with time following placement of Mg(2+)-depleted cells into a buffer containing 1.5 mM magnesium. The uptake rate of Mg2+, d([Mg2+]i)/dt, into Mg(2+)-depleted cells determined with a buffer solution of pH 7.4 was 178 +/- 21 nM/s. Mg2+ uptake at pH 8.0 was markedly increased 278 +/- 35 nM/s, whereas transport at pH 6.0 was significantly reduced to 121 +/- 15 nM/s. Mg2+ uptake at pH 7.4 was not stimulated with 20 or 40 mM bicarbonate, nor were the differences in Mg2+ uptake with pH associated with changes in membrane voltage. Mg2+ uptake was stimulated with membrane hyperpolarization at pH 6.0 but not at pH 8.0. Chlorothiazide (10(-4) M), which stimulates Mg2+ uptake by hyperpolarizing the membrane voltage, increased uptake at pH 6.0, 59 +/- 14%, but decreased it at alkaline pH of 8.0, -55 +/- 3%. Accordingly, MDCT cells become refractory to the stimulating effects of hyperpolarization at alkaline pH values. These studies show that protons may directly affect Mg2+ transport in MDCT cells.

Effects of dDAVP on rat juxtamedullary nephrons: stimulation of medullary K recycling

1985 ◽  
Vol 249 (2) ◽  
pp. F291-F298 ◽  
Author(s):  
J. M. Elalouf ◽  
N. Roinel ◽  
C. de Rouffignac
Keyword(s):  
Parathyroid Hormone ◽  
Adenylate Cyclase ◽  
Excretion Rate ◽  
Distal Tubule ◽  
Fractional Excretion ◽  
The Other ◽  
Thick Ascending Limb ◽  
Adenylate Cyclase System ◽  
Circulating Levels ◽  
Stimulation Of

The effects of 1-desamino-8-D-arginine vasopressin (dDAVP) on the handling of water and electrolytes by the juxtamedullary nephrons were studied on rats with reduced circulating levels of antidiuretic hormone (ADH), parathyroid hormone, calcitonin, and glucagon, all of which stimulate the adenylate cyclase system of the thick ascending limb and the distal tubule. In such hormone-deprived rats and in hormone-deprived + dDAVP rats, the concentration of Na, Cl, and total solutes was lower in the ascending than in the descending limbs, whereas the inulin concentration was similar at both sites. dDAVP did not alter the fraction of NaCl remaining in the thin limbs, but tended to reduce that of Mg and Ca. On the other hand, dDAVP significantly increased the fraction of filtered K remaining from 65.8 +/- 5.2 to 107.3 +/- 15.8%. A direct correlation was observed between the fraction of filtered K remaining at the tip of the juxtamedullary loops and the fractional excretion rate of K in urine. Since dDAVP enhances distal K net secretion, as previously shown in our laboratory, these results indicate that the medullary recycling of K from nephron terminal segments to Henle's loop of juxtamedullary nephrons is stimulated by this peptide.

Glucagon and arginine vasopressin stimulate Mg2+ uptake in mouse distal convoluted tubule cells

1998 ◽  
Vol 274 (2) ◽  
pp. F328-F335 ◽  
Author(s):  
Long-Jun Dai ◽  
Brian Bapty ◽  
Gordon Ritchie ◽  
Gary A. Quamme
Keyword(s):  
Arginine Vasopressin ◽  
Channel Blocker ◽  
Phorbol Esters ◽  
Distal Tubule ◽  
Distal Convoluted Tubule ◽  
Hormone Action ◽  
Camp Pathway ◽  
Tubule Cells ◽  
Free Media ◽  
Stimulation Of

Glucagon and arginine vasopressin (AVP) enhance renal magnesium conservation through actions within the loop of Henle and the distal tubule. Studies were performed on an immortalized mouse distal convoluted tubule (MDCT) cell line to characterize the cellular actions of these hormones on Mg2+transport in this segment of the distal tubule. Glucagon and AVP increased cellular cAMP concentrations by about fivefold above basal levels in normal and Mg2+-depleted cells. Intracellular free Mg2+concentration ([Mg2+]i) was determined on single MDCT cells using microfluorescence with mag-fura 2. To assess Mg2+ uptake, MDCT cells were first Mg2+depleted (0.22 ± 0.01 mM) by culturing in Mg2+-free media for 16 h and then placed in 1.5 mM MgCl2, and the [Mg2+]iwas determined. [Mg2+]ireturned to basal levels, 0.53 ± 0.02 mM, with a mean refill rate, d([Mg2+]i)/d t, of 164 ± 5 nM/s. Both glucagon and AVP stimulated Mg2+ uptake into MDCT cells, 196 ± 11 and 189 ± 6 nM/s, respectively, at concentrations of 3 × 10−7 M and 10−7 M, respectively. Enhanced Mg2+ uptake for each of the hormones was concentration dependent and inhibited by the channel blocker, nifedipine. Hormone stimulation of Mg2+ entry was not dependent on protein synthesis. 8-Bromo-cAMP, 10−4 M, enhanced Mg2+ uptake (225 ± 13 nM/s), whereas phorbol esters were without effect. Finally, protein kinase A inhibition prevented glucagon and AVP stimulation of Mg2+ uptake, supporting the notion that the cAMP pathway is important as expected in the hormone action. These studies demonstrate that glucagon and AVP stimulate Mg2+ uptake in MDCT cells and suggest that these hormones act to control magnesium conservation in the convoluted segment of the distal tubule.

scholarly journals Kctd15 regulates nephron segment development by repressing Tfap2a activity

2020 ◽  
Author(s):  
Brooke E. Chambers ◽  
Eleanor G. Clark ◽  
Allison E. Gatz ◽  
Rebecca A. Wingert
Keyword(s):  
Transcription Factor ◽  
Kidney Development ◽  
Distal Tubule ◽  
Thick Ascending Limb ◽  
Nephron Progenitors ◽  
Nephron Segment ◽  
Feedback Module ◽  
Zebrafish Pronephros ◽  
First Time ◽  
Solute Transporters

AbstractA functional vertebrate kidney relies on structural units called nephrons, which are epithelial tubules that contain a sequence of segments each expressing a distinct repertoire of solute transporters. To date, the transcriptional codes driving regional specification, solute transporter program activation, and terminal differentiation of segment populations remain poorly understood. We demonstrate for the first time that the KCTD15 paralogs, kctd15a and kctd15b, function in concert to restrict distal early (DE)/thick ascending limb (TAL) segment lineage assignment in the developing zebrafish pronephros by repressing Tfap2a activity. During renal ontogeny, expression of these factors co-localized with tfap2a in distal tubule precursors. kctd15 loss primed nephron cells to adopt distal fates by driving expansions in slc12a1, kcnj1a.1, and stc1 marker expression. These phenotypes were resultant of Tfap2a hyperactivity, where kctd15a/b-deficient embryos exhibited increased abundance of this transcription factor. Interestingly, tfap2a reciprocally promoted kctd15 transcription, unveiling a circuit of autoregulation operating in nephron progenitors. Concomitant kctd15b knockdown with tfap2a overexpression produced genetic synergy and further expanded the DE population. Our study provides strong evidence that a transcription factor-repressor feedback module employs tight regulation of Tfap2a and Kctd15 kinetics to control nephron segment fate choice and differentiation during kidney development.

β-Adrenergic agonists stimulate Mg2+ uptake in mouse distal convoluted tubule cells

2000 ◽  
Vol 279 (6) ◽  
pp. F1116-F1123 ◽  
Author(s):  
Hyung Sub Kang ◽  
Dirk Kerstan ◽  
Long-Jun Dai ◽  
Gordon Ritchie ◽  
Gary A. Quamme
Keyword(s):  
Protein Kinase ◽  
Intracellular Signaling ◽  
Distal Tubule ◽  
Distal Convoluted Tubule ◽  
Maximal Response ◽  
Intracellular Camp ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Adrenergic Agonists ◽  
Concentration Dependent Manner

β-Adrenergic agonists influence electrolyte reabsorption in the proximal tubule, loop of Henle, and distal tubule. Although isoproterenol enhances magnesium absorption in the thick ascending limb, it is unclear what effect, if any, β-adrenergic agonists have on tubular magnesium handling. The effects of isoproterenol were studied in immortalized mouse distal convoluted tubule (MDCT) cells by measuring cellular cAMP formation with radioimmunoassays and Mg2+ uptake with fluorescence techniques. Intracellular free Mg2+ concentration ([Mg2+]i) was measured in single MDCT cells by using microfluorescence with mag-fura-2. To assess Mg2+uptake, MDCT cells were first Mg2+ depleted to 0.22 ± 0.01 mM by culturing in Mg2+-free media for 16 h and then placed in 1.5 mM MgCl2, and the changes in [Mg2+]i were determined. [Mg2+]i returned to basal levels, 0.53 ± 0.02 mM, with a mean refill rate, d([Mg2+]i)/d t, of 168 ± 11 nM/s. Isoproterenol stimulated Mg2+ entry in a concentration-dependent manner, with a maximal response of 252 ± 11 nM/s, at a concentration of 10−7 M, that represented a 50 ± 7% increase in uptake rate above control values. This was associated with a sixfold increase in intracellular cAMP generation. Isoproterenol-stimulated Mg2+ uptake was completely inhibited with RpcAMPS, a protein kinase A inhibitor, and U-73122, a phospholipase C inhibitor, and partially blocked by RO 31–822, a protein kinase C inhibitor. Accordingly, isoproterenol-mediated Mg2+ entry rates involve multiple intracellular signaling pathways. Aldosterone potentiated isoproterenol-stimulated Mg2+ uptake (326 ± 31 nM/s), whereas elevation of extracellular Ca2+ inhibited isoproterenol-mediated cAMP accumulation and Mg2+ uptake, 117 ± 37 nM/s. These studies demonstrate that isoproterenol stimulates Mg2+ uptake in a cell line of mouse distal convoluted tubules that is modulated by hormonal and extracellular influences.

Divalent cation transport by the distal nephron: insights from Bartter's and Gitelman's syndromes

2000 ◽  
Vol 279 (4) ◽  
pp. F616-F625 ◽  
Author(s):  
David H. Ellison
Keyword(s):  
Ion Transport ◽  
Divalent Cation ◽  
Urinary Calcium ◽  
Distal Convoluted Tubule ◽  
Calcium Excretion ◽  
Thick Ascending Limb ◽  
Inherited Disease ◽  
Diuretic Drugs ◽  
Tubule Cells ◽  
Phenotypic Features

Elucidation of the gene defects responsible for many disorders of renal fluid and electrolyte homeostasis has provided new insights into normal and abnormal physiology. Identifying the causes of Gitelman's and Bartter's syndromes has greatly enhanced our understanding of ion transport by thick ascending limb and distal convoluted tubule cells. Despite this information, several phenotypic features of these diseases remain confusing, even in the face of molecular insight. Paramount among these are disorders of divalent cation homeostasis. Bartter's syndrome is caused by dysfunction of thick ascending limb cells. It is associated with calcium wasting, but magnesium wasting is usually mild. Loop diuretics, which inhibit ion transport by thick ascending limb cells, markedly increase urinary excretion of both calcium and magnesium. In contrast, Gitelman's syndrome is caused by dysfunction of the distal convoluted tubule. Hypocalciuria and hypomagnesemia are universal parts of this disorder. Yet although thiazide diuretics, which inhibit ion transport by distal convoluted tubule cells, reduce urinary calcium excretion, they have minimal effects on urinary magnesium excretion, when given acutely. This review proposes mechanisms that may account for the differences between the effects of diuretic drugs and the phenotypic features of Gitelman's and Bartter's syndromes. These mechanisms are based on recent insights from another inherited disease of ion transport, inherited magnesium wasting, and from a review of the chronic effects of diuretic drugs in animals and people.

Calcium transport in the nephron

1979 ◽  
Vol 237 (1) ◽  
pp. F1-F6 ◽  
Author(s):  
W. N. Suki
Keyword(s):  
Active Transport ◽  
Calcium Absorption ◽  
Distal Tubule ◽  
Distal Convoluted Tubule ◽  
Thick Ascending Limb ◽  
Passive Mechanism ◽  
Collecting Tubule ◽  
Straight Portion ◽  
Active Calcium ◽  
And Function

Ionized and complexed calcium are filtered at the glomerulus and more than 95% of the filtered load is reabsorbed along the length of the nephron. In the proximal convoluted tubule calcium is absorbed in proportion to sodium and water, suggesting a passive mechanism. The high permeability of this segment is compatible with passive transport, but evidence for active transport has been advanced. A role for Ca2+-ATPase and/or for a Ca2+/Na+ antiport has also been proposed. The straight portion of the proximal tubule appears to transport calcium actively but little is known about the mechanism and regulation of calcium absorption in this segment. Both passive and active transport of calcium in the thick ascending limb have been demonstrated, and heterogeneity in the function of medullary and cortical segments has been proposed. Definite evidence has been advanced for avid active calcium absorption in the distal convoluted tubule. Both chlorothiazide and parathyroid hormone enhance the transport of calcium in this segment. The granular portion of the collecting tubule resembles in its properties and function the distal convoluted tubule. The light portion, however, is incapable of transporting calcium. The distal tubule and collecting tubule may be the final regulators of urinary excretion of calcium but much more data are required before this view can be adopted.

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