scholarly journals Calcium transport through the luminal membrane of the distal tubule. I. Interrelationship with sodium

1992 ◽  
Vol 41 (2) ◽  
pp. 281-288 ◽  
Author(s):  
Michele G. Brunette ◽  
Johanne Mailloux ◽  
Daniel Lajeunesse
Keyword(s):  
Calcium Transport ◽  
Distal Tubule ◽  
Luminal Membrane

Characterization of three types of calcium channel in the luminal membrane of the distal nephron

2004 ◽  
Vol 82 (1) ◽  
pp. 30-37 ◽  
Author(s):  
M G Brunette ◽  
M Leclerc ◽  
D Couchourel ◽  
J Mailloux ◽  
Y Bourgeois
Keyword(s):  
Calcium Transport ◽  
Distal Tubule ◽  
Distal Nephron ◽  
High Affinity ◽  
Luminal Membrane ◽  
Kinetics Of ◽  
Substrate Concentrations ◽  
Renal Calcium Transport ◽  
Specific Inhibitors

We previously reported a dual kinetics of Ca2+ transport by the distal tubule luminal membrane of the kidney, suggesting the presence of several types of channels. To better characterize these channels, we examined the effects of specific inhibitors (i.e., diltiazem, an L-type channel; ω-conotoxin MVIIC, a P/Q-type channel; and mibefradil, a T-type channel antagonist) on 0.1 and 0.5 mM Ca2+ uptake by rabbit nephron luminal membranes. None of these inhibitors influenced Ca2+ uptake by the proximal tubule membranes. In contrast, in the absence of sodium (Na+), the three channel antagonists decreased Ca2+ transport by the distal membranes, and their action depended on the substrate concentrations: 50 µM diltiazem decreased 0.1 mM Ca2+ uptake from 0.65 ± 0.07 to 0.48 ± 0.06 pmol·µg–1·10 s–1 (P < 0.05) without influencing 0.5 mM Ca2+ transport, whereas 100 nM ω-conotoxin MVIIC decreased 0.5 mM Ca2+ uptake from 1.02 ± 0.05 to 0.90 ± 0.05 pmol·µg–1·10 s–1 (P < 0.02) and 1 µM mibefradil decreased it from 1.13 ± 0.09 to 0.94 ± 0.09 pmol·µg–1·10 s–1 (P < 0.05); the latter two inhibitors left 0.1 mM Ca2+ transport unchanged. Diltiazem decreased the Vmax of the high-affinity channels, whereas ω-conotoxin MVIIC and mibefradil influenced exclusively the Vmax of the low-affinity channels. These results not only confirm that the distal luminal membrane is the site of Ca2+ channels, but they suggest that these channels belong to the L, P/Q, and T types.Key words: renal calcium transport, calcium channels, diltiazem, mibefradil, ω-conotoxin.

Luminal influences on potassium secretion: chloride, sodium, and thiazide diuretics

1992 ◽  
Vol 262 (6) ◽  
pp. F1076-F1082 ◽  
Author(s):  
H. Velazquez ◽  
D. H. Ellison ◽  
F. S. Wright
Keyword(s):  
Distal Tubule ◽  
Distal Convoluted Tubule ◽  
Thiazide Diuretics ◽  
Maximal Level ◽  
Luminal Membrane ◽  
K Secretion ◽  
Potassium Secretion

In the presence of Cl-, K+ secretion by the distal tubule saturates with increasing luminal Na+ concentration. Apparent maximal K+ secretion is attained with luminal Na+ concentrations of 40 mM. The results of the present study show that lowering the Cl- concentration of luminal fluid can increase the level of Na(+)-stimulated K+ secretion beyond the maximal level attained in the presence of Cl-. The effect of lowering luminal Cl- concentration to less than 10 mM on K+ secretion is greater with higher Na+ concentration. Under these conditions, chlorothiazide decreases K+ secretion. When chlorothiazide is present, changing the Na+ concentration does not affect K+ secretion. Because in rats a thiazide effect is attributed primarily to the distal convoluted tubule (DCT), we postulate that it is primarily DCT cells that increase K+ secretion when Na+ concentration is raised in the presence of low luminal Cl- concentration. We propose that the rat DCT cells have both an absorptive Na(+)-Cl- cotransport mechanism and a secretory K(+)-Cl- cotransport mechanism in the luminal membrane that can mediate the apparent exchange of Na+ for K+.

Stimulation of distal potassium secretion by low lumen chloride in the presence of barium

1985 ◽  
Vol 248 (5) ◽  
pp. F638-F649 ◽  
Author(s):  
D. H. Ellison ◽  
H. Velazquez ◽  
F. S. Wright
Keyword(s):  
Chloride Concentration ◽  
Distal Tubule ◽  
Perfusion Fluid ◽  
Transport Pathway ◽  
Luminal Membrane ◽  
Potassium Secretion ◽  
Transepithelial Voltage ◽  
Tubule Fluid ◽  
Stimulation Of

Potassium secretion into the renal distal tubule is increased when chloride in the tubule fluid is replaced by another anion. The present experiments were done to determine whether this increment in transported potassium traverses a conductive pathway from cell to lumen. Transport rates of potassium, sodium, chloride, and fluid by the renal distal tubule of rats were examined in vivo by continuous microperfusion. The effects of substituting gluconate for chloride in the presence and absence of 5 mM barium in the perfusion fluid were determined. When gluconate replaced chloride in the perfusion solutions, potassium secretion increased (by 44%) without a significant change in transepithelial voltage. Barium in the lumen increased the magnitude of the lumen-negative transepithelial voltage (by 30%) and reduced potassium secretion (by 56%) by inhibiting conductive potassium movement. Barium also decreased both sodium (by 51%) and chloride (by 37%) absorption. Barium did not reduce the stimulation of potassium secretion caused by reducing lumen chloride concentration. Potassium secretion increased (by 77%) when lumen chloride was reduced in the presence of 5 mM barium. We interpret these results by postulating that a cotransport mechanism linking potassium and chloride is present in the luminal membrane of distal tubule cells, that this mechanism operates in parallel with a conductive transport pathway for potassium, and that the K-Cl cotransport mechanism is not inhibited by barium.

scholarly journals Regulation of the sodium permeability of the luminal border of toad bladder by intracellular sodium and calcium: role of sodium-calcium exchange in the basolateral membrane.

1981 ◽  
Vol 77 (6) ◽  
pp. 693-712 ◽  
Author(s):  
H S Chase ◽  
Q Al-Awqati
Keyword(s):  
Calcium Transport ◽  
Basolateral Membrane ◽  
Intracellular Sodium ◽  
Toad Bladder ◽  
Transepithelial Transport ◽  
Sodium Permeability ◽  
Cell Calcium ◽  
Luminal Membrane ◽  
Sodium Calcium ◽  
Sodium Gradient

Sodium movement across the luminal membrane of the toad bladder is the rate-limiting step for active transepithelial transport. Recent studies suggest that changes in intracellular sodium regulate the Na permeability of the luminal border, either directly or indirectly via increases in cell calcium induced by the high intracellular sodium. To test these proposals, we measured Na movement across the luminal membrane (th Na influx) and found that it is reduced when intracellular Na is increased by ouabain or by removal of external potassium. Removal of serosal sodium also reduced the influx, suggesting that the Na gradient across the serosal border rather than the cell Na concentration is the critical factor. Because in tissues such as muscle and nerve a steep transmembrane sodium gradient is necessary to maintain low cytosolic calcium, it is possible that a reduction in the sodium gradient in the toad bladder reduces luminal permeability by increasing the cell calcium activity. We found that the inhibition of the influx by ouabain or low serosal Na was prevented, in part, by removal of serosal calcium. To test for the existence of a sodium-calcium exchanger, we studied calcium transport in isolated basolateral membrane vesicles and found that calcium uptake was proportional to the outward directed sodium gradient. Uptake was not the result of a sodium diffusion potential. Calcium efflux from preloaded vesicles was accelerated by an inward directed sodium gradient. Preliminary kinetic analysis showed that the sodium gradient changes the Vmax but not the Km of calcium transport. These results suggest that the effect of intracellular sodium on the luminal sodium permeability is due to changes in intracellular calcium.

Physiology and biochemistry of vitamin D-dependent calcium binding proteins

1990 ◽  
Vol 259 (2) ◽  
pp. F195-F209 ◽  
Author(s):  
M. Gross ◽  
R. Kumar
Keyword(s):  
Vitamin D ◽  
Calcium Binding ◽  
Calcium Transport ◽  
Binding Proteins ◽  
Distal Tubule ◽  
Calcium Binding Proteins ◽  
Adult Brain ◽  
Ef Hand ◽  
Physiology And Biochemistry ◽  
The Brain

The vitamin D-dependent calcium binding proteins (calbindins) are members of the troponin-C superfamily of proteins that occur in a number of calcium-transporting tissues such as the intestine, the distal tubule of the kidney, and the placenta. They are also present in other tissues such as the brain, peripheral nervous system, pancreas, parathyroid gland, and bone. In some tissues, such as the adult brain, the proteins occur in the absence of the vitamin. The proteins bind calcium in "EF" hand structures and are "calcium-sensitive" in that they undergo a conformational change on binding calcium. They appear to enhance transcellular calcium transport and are frequently present in tissues that contain the plasma membrane calcium pump.

scholarly journals Conditional Deletion of Fgfr1 in the Proximal and Distal Tubule Identifies Distinct Roles in Phosphate and Calcium Transport

PLoS ONE ◽  
2016 ◽  
Vol 11 (2) ◽  
pp. e0147845 ◽  
Author(s):  
Xiaobin Han ◽  
Jiancheng Yang ◽  
Linqiang Li ◽  
Jinsong Huang ◽  
Gwendalyn King ◽  
...  
Keyword(s):  
Calcium Transport ◽  
Distal Tubule ◽  
Conditional Deletion

Effects of Parathyroid Hormone on Sodium and Calcium Transport in the Dog Nephron

1976 ◽  
Vol 51 (4) ◽  
pp. 345-351 ◽  
Author(s):  
R. A. L. Sutton ◽  
N. L. M. Wong ◽  
J. H. Dirks
Keyword(s):  
Parathyroid Hormone ◽  
Calcium Transport ◽  
Distal Tubule ◽  
Tubular Reabsorption ◽  
Puncture Site ◽  
Calcium Reabsorption ◽  
Renal Tubular Reabsorption ◽  
Renal Tubular ◽  
Selective Enhancement ◽  
Bovine Parathyroid Hormone

1. The effect of purified bovine parathyroid hormone on renal tubular reabsorption of sodium and calcium has been studied by micropuncture in intact and recently thyroparathyroidectomized dogs. 2. Parathyroid hormone increased the rejection of sodium and calcium proportionately at the late proximal tubule in both intact and operated dogs. 3. In both groups of dogs, there was increased delivery of sodium and calcium to the distal tubule after the hormone. However, the Ca/Na ratio decreased, suggesting some selective enhancement of calcium reabsorption before the superficial distal puncture site. 4. In the final urine, the Ca/Na ratio decreased highly significantly in both groups of dogs, indicating a further selective effect of parathyroid hormone on calcium reabsorption in or beyond the distal convoluted tubule.

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