Effects of Intraluminal sulfate on electrolyte transfers along the perfused rat nephron

1981 ◽  
Vol 59 (2) ◽  
pp. 122-130 ◽  
Author(s):  
Gary A. Quamme
Keyword(s):  
Proximal Tubule ◽  
Chloride Transport ◽  
Distal Tubule ◽  
Phosphate Transport ◽  
Loop Of Henle ◽  
Magnesium Transport ◽  
Calcium And Magnesium ◽  
A Site ◽  
Distal Delivery

Superficial nephrons were perfused in vivo to determine the effect of intraluminal sulfate (1–20 mM) on electrolyte reabsorption in the rat with special reference to calcium and magnesium transport. This technique allowed us the opportunity of investigating separate electrolyte transfers without alteration of extrarenal influences. The major amount of perfused sulfate was absorbed in the proximal tubule with little absorption distal to the late proximal collection site. Phosphate transport was not affected by high luminal sulfate concentrations indicating distinct reabsorptive mechanisms for these two anions. Intraluminal sulfate significantly inhibited calcium and magnesium reabsorption in the proximal tubule, loop of Henle, and superficial distal tubule, in distinction to modest effects on sodium transport in these nephron segments. Chloride transport was not altered. The inhibition of divalent cation transfer was not quantitively similar in the different tubule segments. Small amounts of sulfate completely inhibited proximal calcium and magnesium reabsorption with little effect on transport within the loop of Henle. Enhanced distal delivery of sulfate significantly inhibited calcium and magnesium reabsorption in the distal tubule, a site where the sulfate anion is not reabsorbed. These results demonstrate the importance of distal delivery of anionic ligands capable of forming nonreabsorbable complexes. Thus distal calcium and magnesium transport may be greatly modified by proximal control of anion reabsorption.

Effect of furosemide on calcium and magnesium transport in the rat nephron

1981 ◽  
Vol 241 (4) ◽  
pp. F340-F347 ◽  
Author(s):  
G. A. Quamme
Keyword(s):  
Ethacrynic Acid ◽  
Distal Tubule ◽  
Electrolyte Transport ◽  
Loop Of Henle ◽  
Transport Function ◽  
Magnesium Transport ◽  
Henle's Loop ◽  
Calcium And Magnesium ◽  
Single Tubules

Superficial tubules were perfused in vivo to determine the effect of intraluminal furosemide on electrolyte transport in the loop of Henle and distal tubule of the rat with special reference to calcium and magnesium reabsorption. in vivo perfusion of single tubules allowed us the opportunity to investigate separate electrolyte transfers with altering the corticomedullary concentration gradient within the kidney. Intraluminal furosemide (3 X 10(-6) and 3 X 10(-5) M) resulted in proportionately greater calcium and magnesium inhibition relative to sodium and chloride in Henle's loop. Furosemide had little effect on transport function within the perfused superficial distal tubule. Distal calcium and magnesium reabsorption was dependent on their respective deliveries to this segment. Parathyroid hormone increased fractional calcium and magnesium reabsorption in Henle's loop and the distal tubule in the presence of intraluminal furosemide. These results are consistent with a luminal effect of furosemide in the loop of Henle that inhibits calcium and magnesium transport to a greater degree than sodium chloride. Intraluminal ethacrynic acid (10(-4) M) or its cysteine complex had no effect on electrolyte transport in the perfused rat nephron.

Effect of hypercalcemia on renal tubular handling of calcium and magnesium

1982 ◽  
Vol 60 (10) ◽  
pp. 1275-1280 ◽  
Author(s):  
Gary A. Quamme
Keyword(s):  
Urinary Excretion ◽  
Calcium Absorption ◽  
Sodium Absorption ◽  
Loop Of Henle ◽  
Magnesium Transport ◽  
Acute Elevation ◽  
Fractional Calcium Absorption ◽  
Calcium And Magnesium ◽  
Renal Tubular

Tubular calcium and magnesium transport was investigated in thyroparathyroidectomized rats following acute elevation of extracellular calcium concentration. Fractional urinary excretion of calcium increased from 0.2 to 8.3% and magnesium increased from 15 to 39%, while sodium increased modestly from 0.1 to 1.1%. Superficial proximal tubules, Henle's loop, and distal tubules were perfused in vivo to determine the segmental effects of hypercalcemia. Fractional calcium absorption within the loop of Henle was significantly less in the hypercalcemie rats (58%) compared with normal animals (86%). Magnesium transport was inhibited to a greater extent compared with calcium in the loop as the fractional reabsorption decreased from 78% in the normal rats to 35% in the hypercalcemie animals. Sodium absorption was inhibited by 8%. Absolute calcium and magnesium absorption within the superficial distal convoluted tubule increased about three- to four-fold with increased delivery to this segment. These data indicate that hypercalcemia inhibits calcium and magnesium transport relatively more than sodium absorption in the loop of Henle and that this action principally accounts for the increase in urinary excretion of these electrolytes.

Effect of calcitonin on calcium and magnesium transport in rat nephron

1980 ◽  
Vol 238 (6) ◽  
pp. E573-E578 ◽  
Author(s):  
G. A. Quamme
Keyword(s):  
Calcium Concentration ◽  
Transport Model ◽  
Distal Tubule ◽  
Urinary Calcium ◽  
Plasma Calcium ◽  
Loop Of Henle ◽  
Plasma Calcium Concentration ◽  
Calcium And Magnesium ◽  
Magnesium Excretion

Renal calcium and magnesium reabsorption was investigated in young, thyroparathyroidectomized rats receiving synthetic salmon calcitonin. Kidney and tubular function was assessed by clearance and in vivo microperfusion techniques, respectively. Calcitonin reduced urinary calcium and magnesium excretion that was attributed to increased reabsorption within the loop of Henle. This enchanced reabsorption was independent of parathyroid hormone; however, it is contingent on a decline in plasma calcium concentration. Prevention of hypocalcemia by CaCl2 infusion in rats acutely administered calcitonin resulted in loop function comparable to animals not receiving the hormone. Calcitonin had little effect on proximal tubule or distal tubule electrolyte reabsorption. These results are consistent with a transport model for calcium and magnesium in the loop of Henle involving a contraluminal transfer step modulated by absolute extracellular calcium or magnesium. Furthermore, these studies suggest that the discrepancies present in the literature concerning renal effects of calcitonin on electrolyte reabsorption are due to variations in observed hormone action, namely, the effect on plasma calcium concentration.

Intraluminal and contraluminal magnesium on magnesium and calcium transfer in the rat nephron

1980 ◽  
Vol 238 (3) ◽  
pp. F187-F198 ◽  
Author(s):  
G. A. Quamme ◽  
J. H. Dirks
Keyword(s):  
Proximal Tubule ◽  
Plasma Concentrations ◽  
Distal Tubule ◽  
Ringer Solution ◽  
Magnesium Concentration ◽  
Sodium Reabsorption ◽  
Loop Of Henle ◽  
Water Abstraction ◽  
Calcium Reabsorption

Magnesium and calcium transport was studied in the superficial proximal tubule, loop of Henle, and superficial distal tubule of the rat by in vivo microperfusion. Magnesium chloride was used to vary plasma and perfusate magnesium concentration. Perfusion with magnesium-free Ringer solution resulted in little magnesium entry into the tubule lumen in either normomagnesemic or hypermagnesemic rats. Magnesium concentration increased with water abstraction along the perfused proximal tubule whether markedly above or below plasma concentrations. Absolute proximal magnesium reabsorption increased with perfusate concentration; however, fractional magnesium and calcium reabsorption decreased in proportion to net sodium reabsorption with elevated extracellular magnesium. Magnesium absorption increased in the loop of Henle proportional to luminal magnesium concentration. Sodium and calcium reabsorption was not affected. Acute elevation of plasma magnesium, however, significantly depressed absolute magnesium reabsorption to a greater degree than calcium whereas sodium was unchanged. The effects of extracellular magnesium onloop reabsorption were reflected in the final urine. Reabsorption of sodium, calcium, and magnesium in the perfused distal tubule was concentration-dependent and not altered by luminal or extracellular magnesium concentration.

Electrolyte handling by the superficial nephron of the rabbit

1986 ◽  
Vol 250 (4) ◽  
pp. F590-F595 ◽  
Author(s):  
N. L. Wong ◽  
S. J. Whiting ◽  
C. L. Mizgala ◽  
G. A. Quamme
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Concentration Ratio ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Mean Value ◽  
Loop Of Henle ◽  
Collection Site ◽  
Micropuncture Study ◽  
The Mean

A micropuncture study of the rabbit was performed to evaluate the function of the superficial nephron. The mean glomerular filtration rate of the left micropunctured kidney was 4.0 +/- 0.8 ml/min. The concentration profile of electrolytes within the proximal tubule was similar to that of species previously investigated except for potassium. The mean tubular fluid (TF)-ultrafilterable (UF) concentration ratios were as follows: sodium, 1.01 +/- 0.03; chloride, 1.14 +/- 0.04; calcium, 1.12 +/- 0.04; magnesium, 1.47 +/- 0.08; and phosphate, 0.94 +/- 0.09, with a mean TF-plasma (P) inulin concentration ratio of 1.78 +/- 0.14 (n = 32). The TF/UF potassium value significantly increased in association with TF/P inulin to a mean value of 1.26 +/- 0.06. Accordingly, 29% of the filtered potassium was reabsorbed in the superficial proximal tubule compared with 43% of the filtered sodium. The loop of Henle reabsorbed 55-60% of the filtered sodium, chloride, and calcium, whereas considerably less magnesium (33%) was reabsorbed. Segments beyond the distal tubule collection site reabsorbed little of the delivered magnesium, which supports the notion that the loop of Henle is the principal segment accounting for adjustments in magnesium balance. These studies indicate that the superficial nephron of the rabbit performs similar to other species reported, except potassium reabsorption is significantly less in the proximal convoluted tubule.

Absence of estimated glomerular pressure autoregulation during interrupted distal delivery

1975 ◽  
Vol 229 (6) ◽  
pp. 1596-1603 ◽  
Author(s):  
LG Navar ◽  
B Chomdej ◽  
PD Bell
Keyword(s):  
Arterial Pressure ◽  
Proximal Tubule ◽  
Distal Tubule ◽  
Feedback System ◽  
Colloid Osmotic Pressure ◽  
Feedback Mechanism ◽  
Arterial Blood ◽  
Flow Pressure ◽  
Stop Flow ◽  
Distal Delivery

Micropuncture studies in dogs have suggested that a distal tubule-to-afferent arteriole feedback system may participate in the autoregulation mechanism at the single-nephron level. To evaluate the effect of interrupted distal delivery on glomerular capillary pressure (GP) and its autoregulation, the proximal tubule was blocked with oil and maximal stop-flow pressure was measured with a micropressure servo-null system. The GP was estimated from the sum of stop-flow pressure and the plasma colloid osmotic pressure (membrane oncometer). In 18 dogs given a mild mannitol load, average +/- SD control arterial pressure was 118 +/- 16 mmHg, proximal tubule pressure was 24 +/- 5 mmHg, and estimated GP averaged 70 +/- 10 mmHg. There was a highly significant relationship between estimated GP and arterial blood pressure. Similar results were obtained in hydropenic dogs. In response to decreases in renal arterial pressure in individual dogs, stop-flow pressure and estimated GP failed to exhibit autoregulation although autoregulation of renal blood flow, GFR, and proximal tubule pressure was observed over an arterial pressure range of 150-95 mmHg. These results indicate that interruption of normal distal delivery by proximal tubule blockage interferes with the ability of the nephron to autoregulate glomerular pressure. They provide further evidence in support of the concept that a distal tubular feedback mechanism participates, at least in part, in the autoregulatory control of glomerular pressure.

Nephron heterogeneity of phosphate reabsorption: effect of parathyroid hormone

1984 ◽  
Vol 246 (2) ◽  
pp. F155-F158
Author(s):  
A. Haramati ◽  
J. A. Haas ◽  
F. G. Knox
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Distal Tubule ◽  
Proximal Tubules ◽  
Loop Of Henle ◽  
Phosphate Reabsorption ◽  
Phosphate Excretion ◽  
Before And After ◽  
Superficial And Deep Nephrons ◽  
Nephron Heterogeneity

We evaluated the response of superficial and deep nephron proximal tubules to PTH in thyroparathyroidectomized (TPTX) rats fed a normal phosphate diet (0.7%). As phosphate reabsorption is not detectable in the ascending limb of the loop of Henle, fractional phosphate delivery (FDPi%) to the superficial early distal tubule and papillary loop of Henle reflects delivery from superficial and deep nephron proximal tubules, respectively. Re-collection micropuncture experiments were performed in nine acutely TPTX rats before and after the infusion of PTH (33 U/kg bolus; 1 U X kg-1 X min-1). In response to PTH, fractional phosphate excretion increased from 3.3 to 26.2% (P less than 0.05). FDPi% was less from the deep than from the superficial proximal tubule (5.7 vs. 15.7%, P less than 0.05) prior to PTH, indicating enhanced phosphate reabsorption by deep compared with superficial proximal tubules. During PTH infusion, FDPi% was increased in both nephron groups compared with control (P less than 0.05), but there were no differences in phosphate delivery between deep (28.0%) and superficial (29.7%) proximal tubules. We conclude that in acutely volume-expanded TPTX rats, infusion of a pharmacologic dose of PTH decreases phosphate reabsorption in both superficial and deep nephrons. Furthermore, the heterogeneity of FDPi% from deep compared with superficial proximal tubules seen in TPTX rats is absent during PTH infusion.

Effects of acid-base disturbances on renal handling of magnesium in the dog

1986 ◽  
Vol 70 (3) ◽  
pp. 277-284 ◽  
Author(s):  
Norman L. M. Wong ◽  
Gary A. Quamme ◽  
John H. Dirks
Keyword(s):  
Metabolic Acidosis ◽  
Proximal Tubule ◽  
Indirect Effect ◽  
Metabolic Alkalosis ◽  
Distal Tubule ◽  
Acid Base ◽  
Renal Handling ◽  
Chronic Metabolic Acidosis ◽  
Magnesium Transport

1. Clearance and micropuncture studies were performed in four groups of acutely thyropara-thyroidectomized animals to study the effects of alkalosis and acidosis on the renal handling of magnesium. 2. Our results indicate that chronic metabolic acidosis reduces, whereas acute metabolic alkalosis enhances, magnesium reabsorption. 3. The site within the nephron where absorption of magnesium increases or decreases during acid-base disturbances was beyond the late proximal tubule. 4. Tubular fluid bicarbonate was also measured in these experiments, and the results indicated that magnesium reabsorption in the distal tubule correlated to bicarbonate delivery. However, whether this was a direct or an indirect effect of bicarbonate on magnesium transport could not be delineated.

Effects of parathyroid hormone on electrolyte transport in the hamster nephron

1979 ◽  
Vol 236 (4) ◽  
pp. F342-F348 ◽  
Author(s):  
C. A. Harris ◽  
M. A. Burnatowska ◽  
J. F. Seely ◽  
R. A. Sutton ◽  
G. A. Quamme ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Distal Tubule ◽  
Electrolyte Transport ◽  
Puncture Site ◽  
Phosphate Reabsorption ◽  
Renal Electrolyte Transport ◽  
Clearance Studies ◽  
Calcium And Magnesium

Recollection micropuncture and clearance studies were carried out on thyroparathyroidectomized hamsters to clarify the localization of the effects of parathyroid hormone (PTH) on renal electrolyte transport. The clearance data confirmed that PTH inhibits phosphate and enhances calcium and magnesium reabsorption. These effects appeared to result from actions of the hormone in several parts of the nephron. In the proximal tubule PTH did not affect H2O reabsorption but inhibited phosphate reabsorption ((TF/P)PO4 increased from 0.46 +/- 0.04 to 0.57 +/- 0.03, P less than 0.02) and appeared to enhance calcium and magnesium reabsorption ((TF/UF)Ca decreased from 1.41 +/- 0.07 to 1.25 +/- 0.06, P less than 0.001, and (TF/UF)Mg from 1.66 +/- 0.10 to 1.51 +/- 0.08, P less than 0.05; in control animals (TF/UF)Ca increased from 1.51 +/- 0.10 to 1.65 +/- 0.11, P less than 0.01). PTH further inhibited phosphate reabsorption and enhanced calcium and magnesium reabsorption between the late proximal and early distal sites of puncture. Comparison of fractional deliveries of calcium and magnesium from the late distal tubule with their fractional excretions suggests an additional effect beyond the distal puncture site. The phosphaturic, but not the calcium- and magnesium-retaining, effects of PTH were abolished by a 16-h fast.

Effect of volume expansion with NaCl or NaHCO3 on nephron fluid and Cl transport

1977 ◽  
Vol 233 (2) ◽  
pp. F118-F125
Author(s):  
J. H. Galla ◽  
J. E. Beaumont ◽  
R. G. Luke
Keyword(s):  
Proximal Tubule ◽  
Plasma Volume ◽  
Sodium Excretion ◽  
Volume Expansion ◽  
Chloride Transport ◽  
Loop Of Henle ◽  
Fluid Reabsorption ◽  
Micropuncture Technique ◽  
Chloride Excretion ◽  
Anion Composition

To assess the influence of plasma anions on nephron fluid and chloride transport following volume expansion (VE), rats were studied by micropuncture technique during hydropenia and after VE with NaCl (CVE) or NaHCO3 (BVE). VE with either solution produced increments in plasma volume, SNGFR, and fractional sodium excretion (FENa), and decrements in proximal and distal TF/P inulin ratio which were not different. The proximal transepithelial chloride ratio decreased similarly in CVE (from 1.34 to 1.16) and BVE (from 1.32 to 1.17). Following VE, proximal fractional Cl reabsorption decreased similarly in both CVE (-5.9%) and BVE (-7.4%). Early distal fractional Cl reabsorption also was decreased in CVE (-12%) but not in BVE (-1%). Fractional chloride excretion increased in CVE but not in BVE. Therefore, following VE plasma anion composition did not significantly modify either fluid reabsorption in proximal tubule or loop of Henle or urinary Na excretion. The fraction of sodium reabsorbed with chloride in the proximal tubule increased, and Cl conservation, primarily within the loop of Henle, can be maintained despite marked natriuresis.

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