Micropuncture investigations on the effect of angiotensin on the inorganic phosphate reabsorption in the proximal tubule of the rat

1973 ◽  
Vol 342 (1) ◽  
pp. 73-82 ◽  
Author(s):  
D. Gekle ◽  
B. von Carlowitz ◽  
U. Geisel
Keyword(s):  
Proximal Tubule ◽  
Inorganic Phosphate ◽  
Phosphate Reabsorption ◽  
Inorganic Phosphate Reabsorption

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.

scholarly journals Metabolic Requirement for Inorganic Phosphate by the Rabbit Proximal Tubule

1982 ◽  
Vol 70 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Peter C. Brazy ◽  
Steven R. Gullans ◽  
Lazaro J. Mandel ◽  
Vincent W. Dennis
Keyword(s):  
Proximal Tubule ◽  
Inorganic Phosphate ◽  
Metabolic Requirement

scholarly journals Effect of propranolol on phosphate reabsorption by superficial nephron segments in response to parathyroid hormone in phosphate-deprived rats.

1990 ◽  
Vol 1 (2) ◽  
pp. 200-204
Author(s):  
A Rybczynska ◽  
A Hoppe ◽  
F G Knox
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Distal Tubule ◽  
Free Flow ◽  
Phosphate Deprivation ◽  
Phosphate Reabsorption ◽  
Nephron Segments ◽  
Pars Recta

Phosphate deprivation causes a resistance to the phosphaturic effect of parathyroid hormone. The decreased phosphaturic response to parathyroid hormone in rats fed a low phosphate diet for 1 day can be restored by propranolol infusion. Free-flow micropuncture studies were performed to localize the nephron site of restoration of the phosphaturic effect of parathyroid hormone by propranolol in rats deprived of phosphate for one day. In animals fed low phosphate diet and in the presence of parathyroid hormone, propranolol infusion did not change phosphate delivery to the late proximal tubule; however, fractional delivery of phosphate to the early distal tubule was significantly increased from 18.3 +/- 2.9 to 32.2 +/- 4.1%. In rats fed a normal phosphate diet, propranolol infusion did not change phosphate delivery along the nephron. We conclude that the restoration of the phosphaturic effect of parathyroid hormone by propranolol infusion in rats deprived of phosphate for 1 day is primarily due to decreased reabsorption of phosphate by superficial loop segments, most likely the pars recta segment of the proximal tubule.

Proximal tubule site of inhibition of phosphate reabsorption by calcitonin

1984 ◽  
Vol 246 (6) ◽  
pp. F927-F930 ◽  
Author(s):  
T. J. Berndt ◽  
F. G. Knox
Keyword(s):  
Proximal Tubule ◽  
Salmon Calcitonin ◽  
Distal Tubule ◽  
Proximal Convoluted Tubule ◽  
Phosphate Reabsorption

The present study was performed to evaluate the nephron site of inhibition by calcitonin of phosphate reabsorption in the thyroparathyroidectomized rat. Pharmacologic doses of salmon calcitonin markedly inhibited fluid and phosphate reabsorption by the superficial proximal tubule. However, continued phosphate reabsorption between the superficial late proximal and early distal tubule, as well as along the distal tubule, blunted the phosphaturic effect of calcitonin. We conclude that the phosphaturic effect of a pharmacologic dose of salmon calcitonin is primarily due to an inhibition of fluid and phosphate reabsorption by the proximal convoluted tubule.

Tubular handling of Pi: localization of effects of 1,25(OH)2D3 and dietary Pi in TPTX rats

1981 ◽  
Vol 241 (2) ◽  
pp. F123-F128
Author(s):  
R. C. Muhlbauer ◽  
J. P. Bonjour ◽  
H. Fleisch
Keyword(s):  
Proximal Tubule ◽  
Inorganic Phosphate ◽  
Distal Tubule ◽  
Chronic Administration ◽  
Terminal Portion ◽  
Dihydroxyvitamin D3 ◽  
Reabsorptive Capacity ◽  
Clearance Studies ◽  
Early Portion ◽  
The Difference

Previous clearance studies have shown that chronic administration (26 pmol/day i.p. for 7 days) of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) decreases the tubular reabsorptive capacity for inorganic phosphate (Pi) in thyroparathyroidectomized (TPTX) rats. In the present study the tubular localization of this effect was examined by free-flow micropuncture in TPTX rats. At the mentioned dosage, 1,25(OH)2D3 inhibited net Pi reabsorption in the early portion of the proximal tubule. In addition, 1,25(OH)2D3 treatment altered the difference in Pi delivery between the distal tubule and the final urine, suggesting an inhibition of net Pi reabsorption along the terminal portion of the nephron, or, alternatively, admixture of tubular fluid with higher Pi concentration from deep nephrons. Finally, in TPTX rats the tubular localization of the effect of varying the dietary Pi content was found to be quite similar to that of 1,25(OH)2D3.

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