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.

Micropuncture study of the superficial nephron of Perognathus penicillatus

1981 ◽  
Vol 241 (6) ◽  
pp. F612-F617
Author(s):  
E. J. Braun ◽  
D. R. Roy ◽  
R. L. Jamison
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Urine Osmolality ◽  
Small Rodent ◽  
Micropuncture Study ◽  
Single Nephron ◽  
Average Body

A micropuncture study of Perognathus penicillatus, a small rodent native to the deserts of the southwestern United States was performed to evaluate the function of the superficial nephron. Data are reported for 12 animals of 17 g average body wt. Mean glomerular filtration rate was 475 +/- 73 microliter X min-1 X g kidney wt-1. Urine osmolality averaged 1,154 +/- 197 mosmol/kg H2O. Single nephron glomerular filtration rate averaged 43 nl X min-1 X g kidney wt-1 in the proximal tubule and 48 in the distal tubule, values that are not significantly different. In terms of the filtered load remaining unreabsorbed at the end of the accessible proximal tubule, the average percentages were 46 water, 48 total solute, 45 sodium, 56 phosphorus, 62 potassium, 71 magnesium, and 54 calcium. The concentrations of potassium and magnesium in fluid samples increased significantly along the proximal tubule. Approximately at the midpoint of the distal tubule, fractional delivery of water, 13.1%, was greater than that for total solute, 10%, or sodium, 7%, indicating that the intervening segment of nephron reabsorbed solute and sodium in excess of water. The function of the superficial nephron resembles that of species previously investigated except for potassium reabsorption in the proximal convoluted tubule.

Effects of blood pH changes on potassium excretion in the dog

1962 ◽  
Vol 202 (4) ◽  
pp. 768-772 ◽  
Author(s):  
Charles Toussaint ◽  
Pierre Vereerstraeten
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Excretion Rate ◽  
Distal Tubule ◽  
Potassium Excretion ◽  
Ph Changes ◽  
Blood Ph ◽  
Ph Level

K+ excretion rate was measured at normal as well as at rising plasma K+ concentration in intact, in K-depleted, and in acetazolamide-treated dogs submitted to acute blood pH changes. The results indicate that, for any given value of glomerular filtration rate, K+ excretion rate is determined by at least three factors: 1) plasma K+ concentration, 2) blood pH level, and 3) presumably, the H+ gradient across the luminal border of the distal tubule. The data further suggest that most of the filtered K+ is reabsorbed by the proximal tubule, even in conditions of high filtered loads.

Cisplatin nephrotoxicity in rats: defect in papillary hypertonicity

1981 ◽  
Vol 241 (2) ◽  
pp. F175-F185 ◽  
Author(s):  
R. Safirstein ◽  
P. Miller ◽  
S. Dikman ◽  
N. Lyman ◽  
C. Shapiro
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Collecting Duct ◽  
Urine Volume ◽  
Distal Tubule ◽  
Urine Osmolality ◽  
Solute Content ◽  
Cisplatin Nephrotoxicity

We examined the effects of cisplatin (5 mg/kg BW) on renal function in rats. Three days after administration of cisplatin whole kidney clearance of inulin fell and 24-h urine volume increased. Maximal urine osmolality and papillary solute content were reduced. Superficial nephron glomerular filtration rate measured along the proximal tubule, where no leak of inulin could be demonstrated, was reduced in cisplatin-treated animals. Differences between superficial nephron glomerular filtration rate determined in proximal and distal tubules were greater in cisplatin-treated rats than in control rats. Neither a change in fluid or sodium movement along superficial nephrons nor a reduced early distal tubule transepithelial sodium gradient explain the polyuria. Urea was reabsorbed from, not added to, the loop fluid in cisplatin-treated animals. Morphologic changes were evident in the S3 segment of the proximal tubule in cisplatin-treated animals but the glomeruli were normal. Polyuria occurred despite diminished glomerular filtration rate in cisplatin nephrotoxicity. The diminished concentration of salt and urea in the papilla as a result of abnormal function of the collecting duct or pars recta portion of the proximal tubule contributed to the defect in concentrating ability.

Change in Glomerular Filtration Rate with Febuxostat in Patients with Advanced Chronic Renal Failure

2021 ◽  
Vol 15 (11) ◽  
pp. 3293-3295
Author(s):  
Ishtiaq Alam ◽  
Faheem Usman Sulehri ◽  
Muhammad Abdul Azim Baig ◽  
Maira Bhatti ◽  
Fouzia Perveen ◽  
...  
Keyword(s):  
Glomerular Filtration Rate ◽  
Kidney Disease ◽  
Serum Creatinine ◽  
Serum Creatinine Level ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Estimated Glomerular Filtration Rate ◽  
Mean Value ◽  
Kidney Dysfunction ◽  
The Mean

Background: Chronic kidney disease (CKD), is defined as progressive loss in kidney function. The study evaluated the mean change in estimated glomerular filtration rate (eGFR) with febuxostat in patients of advanced chronic kidney dysfunction with hyperuricemia. Methodology: A prospective observational study was conducted at the department of Nephrology, Sheikh Zayed Hospital, Lahore for 6 months, from January 2019 to October 2019. At baselines, the blood sample was obtained and sent to the laboratory for assessment of serum creatinine level. The eGFR was calculated by using the MDRD formula. Patients were then advised to take one oral Febuxostat 40 mg daily for 6 months. After 6 months, the blood sample was obtained for assessment of serum creatinine level. Results: The mean age of the patients was 40.72±14.90 years, male to female ratio was 1:1. The mean value of eGFR at baseline was 23.53±11.09 and its mean value at 6th month was 34.28+12.31, which was significant (p<0.001). Conclusion: Febuxostat effectively improved estimated glomerular filtration rate (eGFR) in patients presenting with advanced chronic kidney dysfunction with hyperuricemia. Keywords: Hyperuricemia, Kidney, Disease, Febuxostat, Dysfunction, Glomerular, Filtration

Chlorothiazide effect on feedback-mediated control of glomerular filtration rate

1989 ◽  
Vol 257 (1) ◽  
pp. F137-F144 ◽  
Author(s):  
M. D. Okusa ◽  
A. E. Persson ◽  
F. S. Wright
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Feedback System ◽  
Sprague Dawley ◽  
Single Nephron ◽  
The Difference ◽  
Tubule Fluid

We examined the effect of chlorothiazide (CTZ) on the tubuloglomerular (TG) feedback system in anesthetized Sprague-Dawley rats. During infusion of CTZ (0.25 mg.kg body wt-1.min-1) we found that whole kidney glomerular filtration rate (GFR) decreased by 19% (1.0 +/- 0.1 vs. 0.8 +/- 0.1 ml/min; P less than 0.005). To asses the activity of the TG feedback system during CTZ administration we compared measurements of single-nephron (SN)GFR from tubule fluid sampled separately at proximal and distal sites. During CTZ administration, distally measured SNGFR decreased significantly by 16% (27.3 +/- 1.3 vs. 22.9 +/- 1.1 nl/min; P less than 0.025), whereas proximally measured SNGFR was unchanged. Thus the difference in SNGFR between proximal and distal determination increased during CTZ infusion (4.7 +/- 0.7 vs. 7.7 +/- 0.7 nl/min; P less than 0.025), indicating that CTZ suppresses GFR by TG feedback. Na, K, and Cl concentrations measured in the late proximal tubule fluid during control and CTZ infusions were similar. In early distal tubule fluid samples K and Cl concentrations were unaffected by CTZ infusion, whereas Na concentrations increased by 32% (47.9 +/- 2.7 vs. 63.1 +/- 2.4 mM; P less than 0.001). Proximal tubule microperfusion with 1.0 mM CTZ decreased transport rates of Na and water by approximately 40%, whereas the transport rate of Cl was not affected. In conclusion our results indicate that CTZ reduces GFR by activating TG feedback. The mechanism by which this occurs is in part due to an increase in the strength of the signal.

Mechanism of the Impaired Natriuretic Response to Frusemide during Sodium Depletion: A Micropuncture Study in Rats

1996 ◽  
Vol 91 (3) ◽  
pp. 299-305 ◽  
Author(s):  
D. G. Shirley ◽  
S. J. Walter ◽  
R. J. Unwin
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Inhibitory Effect ◽  
Sodium Reabsorption ◽  
Loop Of Henle ◽  
Sodium Depletion ◽  
Anaesthetized Rats ◽  
Proximal Tubular

1. The nephron sites involved in the blunted natriuretic response to frusemide during sodium depletion were investigated using micropuncture techniques in anaesthetized rats. 2. Glomerular filtration rate was lower, and fractional sodium reabsorption in the proximal convoluted tubule higher, in sodium-depleted than in sodium-replete rats. Consequently, sodium delivery to the loop of Henle was reduced (by approximately 35%) in the sodium-depleted animals. Intravenous frusemide (2.5 mg h−1 kg−1; urinary water and electrolyte losses replaced) had no effect on glomerular filtration rate or proximal tubular sodium reabsorption in either group. 3. The inhibitory effect of intravenous frusemide on fractional sodium reabsorption in the nephron segments constituting the loop of Henle (measured by free-flow micropuncture) was attenuated during sodium depletion. However, when loops of Henle were microperfused at identical rates with artificial late proximal tubular fluid, no difference in the responses of sodium-depleted and sodium-replete rats to intraluminal frusemide (10−5 mol/l) could be detected. 4. In sodium-replete animals, the increased load of sodium delivered from the loop of Henle during frusemide administration resulted in a lowering of fractional sodium reabsorption in the distal tubule. In contrast, in sodium-depleted rats given frusemide, fractional distal sodium reabsorption tended to increase, so that values in the two groups of frusemide-treated animals were markedly different (0.30 ±0.04 versus 0.51 ±0.03). 5. It is concluded that the blunted natriuretic response to frusemide during sodium depletion results from at least three factors: a reduced sodium delivery to the loop of Henle; a reduced inhibitory effect of frusemide on fractional sodium reabsorption in the loop of Henle, which may be a consequence of the reduced sodium load; and enhanced fractional reabsorption of sodium in the distal tubule, which partially buffers the diuretic-induced increase in sodium delivery from the loop.

Developmental pattern of water and electrolyte transport in rat superficial nephrons

1983 ◽  
Vol 245 (1) ◽  
pp. F15-F21 ◽  
Author(s):  
M. Lelievre-Pegorier ◽  
C. Merlet-Benichou ◽  
N. Roinel ◽  
C. de Rouffignac
Keyword(s):  
Proximal Tubule ◽  
Concentration Gradient ◽  
Electron Probe ◽  
Concentration Ratio ◽  
Adult Animal ◽  
Loop Of Henle ◽  
Age Group ◽  
The Mean ◽  
Sodium And Potassium ◽  
Plasma Ultrafiltrate

Micropuncture samples were collected from late proximal and early distal sites of the same nephron in nondiuretic young rats aged 13-15, 19-21, and 30-39 days. Plasma ultrafiltrate (UF), tubular fluid (TF), and final urine were analyzed for Cl, Na, K, Mg, P, and Ca concentrations by electron probe. Between days 13 and 39, the proximal convoluted tubule reabsorbed a constant fraction of continuously increasing filtered loads of water, sodium, and potassium. The mean TF/UF concentration ratio for Cl in the late proximal tubule was 0.98 +/- 0.03 in the 13- to 15-day age group and increased to 1.20 +/- 0.03 in the 30- to 39-day age group. The mean TF/UF concentration ratio for Mg increased from 1.17 +/- 0.07 at 13-15 days to 2.07 +/- 0.22 at 30-39 days. The mean TF/UF concentration ratio for Ca at the end of the proximal tubule was found to be significantly lower than unity in the two youngest groups and higher in the oldest. Evidence was also found for maturation of the loop of Henle. The amounts of Cl, Na, K, and Ca reabsorbed by the loop, expressed in percent of the amount delivered, rose significantly with age. In contrast, mean Mg fractional reabsorption was already maximal in the youngest group. Phosphate reabsorption in the loop was limited in all three groups. It is concluded that in the 13- to 15-day rats 1) the fraction of the Na, K, and H2O filtered loads reabsorbed along the proximal tubule is already the same as in adult animals; 2) the proximal tubule epithelium is not able to create or maintain a transepithelial concentration gradient for Cl; and 3) the fractional reabsorption of Mg is higher than in the adult animal. It is also concluded that Cl, Na, K, and Ca transport along the loop of Henle all have the same maturation pattern but that the pattern for Mg is different.

The Mode of Excretion of Ammonia and Urea in Xenopus Laevis

1961 ◽  
Vol 38 (4) ◽  
pp. 695-705
Author(s):  
J. B. BALINSKY ◽  
E. BALDWIN
Keyword(s):  
Xenopus Laevis ◽  
Blood Concentration ◽  
Concentration Ratio ◽  
Ammonia Excretion ◽  
Ammonia Concentration ◽  
Mean Value ◽  
Urea Excretion ◽  
Wide Range ◽  
Glomerular Filtrate ◽  
The Mean

1. Eighty-two single determinations of ammonia and urea excretion by Xenopus laevis indicated that the percentage of ammonia varied from 40 to 80%, with a mean value of 62%. 2. Measurements of excretion on successive days after feeding showed that a large amount of ammonia was produced soon after feeding, but that ammonia excretion declined rapidly. Urea excretion, not so high initially, remained more or less constant until the third or fourth day, often exceeding ammonia excretion at that time. Thereafter, it also declined and the excretion of both substances reached a constant starvation level by the fifteenth day. 3. Both ammonia and urea excretion were equally affected by temperature. The Q10's were near 2 in the range 20-30° C., but greater in the range 10-20° C. 4. At least 86% of ammonia, and 81% of urea were excreted through the cloaca. 5. The mean 24 hr. urine output of Xenopus at 20% C. was 23.6 ml. per 100 g. body weight. 6. Although the blood ammonia concentration did not appear to be zero, the urine/blood concentration ratio of ammonia was greater than 100. The urine/blood concentration ratio of urea was not significantly different from unity, and constant over a very wide range of concentrations. 7. The above result is interpreted to indicate passive glomerular filtration of urea, and little or no tubular reabsorption of water. 8. It is suggested that ammonia is formed in the kidney, and actively secreted into the glomerular filtrate.

Micropuncture analysis of single-nephron function in NHE3-deficient mice

1999 ◽  
Vol 277 (3) ◽  
pp. F447-F453 ◽  
Author(s):  
John N. Lorenz ◽  
Patrick J. Schultheis ◽  
Timothy Traynor ◽  
Gary E. Shull ◽  
Jürgen Schnermann
Keyword(s):  
Proximal Tubule ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Transport Processes ◽  
Tubuloglomerular Feedback ◽  
Thick Ascending Limb ◽  
Fluid Reabsorption ◽  
Fluid Delivery ◽  
Single Nephron ◽  
Flow Pressure

The Na/H exchanger isoform 3 (NHE3) is expressed in the proximal tubule and thick ascending limb and contributes to the reabsorption of fluid and electrolytes in these segments. The contribution of NHE3 to fluid reabsorption was assessed by micropuncture in homozygous ( Nhe3 −/−) and heterozygous ( Nhe3 +/−) knockout mice, and in their wild-type (WT, Nhe3 +/+) littermates. Arterial pressure was lower in the Nhe3 −/−mice (89 ± 6 mmHg) compared with Nhe3 +/+ (118 ± 4) and Nhe3 +/−(108 ± 5). Collections from proximal and distal tubules demonstrated that proximal fluid reabsorption was blunted in both Nhe3 +/− and Nhe3 −/−mice (WT, 4.2 ± 0.3; Nhe3 +/−, 3.4 ± 0.2; and Nhe3 −/−, 2.6 ± 0.3 nl/min; P < 0.05). However, distal delivery of fluid was not different among the three groups of mice (WT, 3.3 ± 0.4 nl/min; Nhe3 +/−, 3.3 ± 0.2 nl/min; and Nhe3 −/−, 3.0 ± 0.4 nl/min; P < 0.05). In Nhe3 −/−mice, this compensation was largely attributable to decreased single-nephron glomerular filtration rate (SNGFR): 10.7 ± 0.9 nl/min in the Nhe3 +/+ vs. 6.6 ± 0.8 nl/min in the Nhe3 −/−, measured distally. Proximal-distal SNGFR differences in Nhe3 −/−mice indicated that much of the decrease in SNGFR was due to activation of tubuloglomerular feedback (TGF), and measurements of stop-flow pressure confirmed that TGF is intact in Nhe3 −/−animals. In contrast to Nhe3 −/−mice, normalization of early distal flow rate in Nhe3 +/−mice was not related to decreased SNGFR (9.9 ± 0.7 nl/min), but rather, to increased fluid reabsorption in the loop segment ( Nhe3 +/+, 2.6 ± 0.2; Nhe3 +/−, 3.6 ± 0.5 nl/min). We conclude that NHE3 is a major Na/H exchanger isoform mediating Na+ and fluid reabsorption in the proximal tubule. In animals with NHE3 deficiency, normalization of fluid delivery to the distal tubule is achieved through alterations in filtration rate and/or downstream transport processes.

Renal glomerular filtration rate and hepatic blood flow during voluntary diving in Weddell seals

1983 ◽  
Vol 245 (5) ◽  
pp. R743-R748 ◽  
Author(s):  
R. W. Davis ◽  
M. A. Castellini ◽  
G. L. Kooyman ◽  
R. Maue
Keyword(s):  
Blood Flow ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Hepatic Blood Flow ◽  
Filtration Rate ◽  
Hepatic Function ◽  
Inulin Clearance ◽  
Weddell Seals ◽  
Icg Clearance ◽  
The Mean

Renal and hepatic function were studied during voluntary dives in Weddell seals by measuring the clearance rate of inulin and indocyanine green (ICG). Inulin is cleared exclusively by the kidneys and measures renal glomerular filtration rate (GFR). ICG is cleared by the liver and is blood flow dependent at concentrations used. Studies were conducted from a portable hut with a trapdoor placed over an isolated hole in the sea ice near McMurdo Station, Antarctica. An intravertebral extradural catheter was inserted percutaneously under light anesthesia in subadult seals weighing 130-200 kg. When released into the ice hole, the seals made voluntary dives, but always had to return to breathe. Serial blood samples were taken after single injections of inulin and ICG and analyzed within 24 h. The mean half time (t 1/2) for inulin clearance while resting at the surface was 27.3 +/- 13.0 min (n = 43) and the mean t 1/2 for ICG clearance was 18.3 +/- 7.3 min (n = 23). The mean resting GFR was 3.6 ml X min-1 X kg-1 (range 3.2-3.9, n = 3). Inulin and ICG clearance rates did not change from resting levels during dives shorter than the seal's aerobic dive limit (ADL). Inulin clearance decreased over 90% during dives longer than the ADL, but there was no significant reduction in ICG clearance during dives lasting up to 23 min. It appears that normal renal GFR and hepatic blood flow continue during natural aerobic dives. During dives that exceed the ADL, GFR is reduced but hepatic blood flow may be maintained.

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