Nephron filtration rate in conscious rats recovering from anesthesia

1977 ◽  
Vol 232 (4) ◽  
pp. F329-F334
Author(s):  
J. P. Bonvalet ◽  
M. Champion ◽  
F. Wanstok ◽  
G. Berjal
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Experimental Conditions ◽  
Nephron Filtration Rate ◽  
Conscious Rats ◽  
Anesthetized Rats ◽  
Saline Loading ◽  
Single Nephron ◽  
Infusion Technique

Single-nephron glomerular filtration rate (SNGFR) of superficial (S) and juxtamedullary (JM) nephrons was measured in conscious rats with a [14C]ferrocyanide infusion technique. Experiments were carried out in nondiuretic (ND), salt-loaded (SL), and hemorrhagic hypotensive (HH) rats. Mean SNGFR values of S and JM nephrons were 48.7 +/- 4.5 SE and 61.7 +/- 4.2 in ND, 73.6 +/- 8.7 and 87.5 +/- 10.8 in SL, and 29.9 +/- 5.9 and 36.4 +/- 7.1 in HH rats. These values are higher than the values reported in anesthetized rats. The S-to-JM SNGFR ratio was not significantly different in the three experimental conditions (ND, 0.788 +/- 0.032; SL, 0.843 +/- 0.018; and HH, 0.824 +/- 0.030), and did not differ from the values reported in anesthetized rats in similar experimental conditions. It is concluded that anesthesia exerts a depressive effect on GFR, but does not modify intrarenal SNGFR distribution. Neither saline loading nor hemorrhagic hypotension induces SNGFR intrarenal redistribution in conscious rats.

Abnormalities in glomerular function in rats developing spontaneous hypertension

1984 ◽  
Vol 246 (1) ◽  
pp. F12-F20 ◽  
Author(s):  
J. R. Dilley ◽  
C. T. Stier ◽  
W. J. Arendshorst
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Fluid Collection ◽  
Spontaneously Hypertensive ◽  
Fluid Delivery ◽  
Fluid Load ◽  
Single Nephron ◽  
Wistar Kyoto ◽  
Ultrafiltration Pressure

Clearance and micropuncture studies were conducted on 6-wk-old spontaneously hypertensive rats (SHR) of the Okamoto-Aoki strain and normotensive Wistar-Kyoto rats (WKY) under euvolemic conditions. Mean arterial pressure in SHR was elevated by 18 mmHg and their kidneys were vasoconstricted with reduced blood flow; resistances in preglomerular vessels and efferent arterioles were elevated 2.8 and 2 times, respectively, above WKY values. Whole kidney glomerular filtration rate (GFR) and single nephron glomerular filtration rate (SNGFR), based on fluid collection from either proximal or distal convolutions, were 25-30% lower in SHR. Fractional reabsorptions of fluid load by the proximal convoluted tubule (43%) and by the loop of Henle (52-55%) were similar in both groups. Accordingly, SHR exhibited less fluid delivery from the proximal convolution (8 vs. 12 nl/min) and to the distal convolution (3 vs. 5 nl/min). Glomerular dynamics in hypertensive and normotensive strains were characterized by filtration pressure disequilibrium. Estimated glomerular capillary pressure and mean effective ultrafiltration pressure were similar in SHR and WKY. SHR had a lower glomerular ultrafiltration coefficient than WKY (0.011 vs. 0.016 nl X s-1 X mmHg-1), which, combined with a lower glomerular plasma flow (41 vs. 73 nl/min), quantitatively accounted for the lower SNGFR in 6-wk-old SHR. These findings document important differences in renal function in young SHR compared with WKY that may participate in the development of hypertension.

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.

Neurogenic regulation of proximal bicarbonate and chloride reabsorption

1986 ◽  
Vol 250 (1) ◽  
pp. F22-F26 ◽  
Author(s):  
M. G. Cogan
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Sprague Dawley ◽  
Electrolyte Excretion ◽  
Nerve Activity ◽  
Renal Nerve ◽  
Single Nephron ◽  
Renal Nerve Activity ◽  
Chloride Excretion

Although a change in renal nerve activity is known to alter proximal reabsorption, it is unclear whether reabsorption of NaHCO3 or NaCl or both are affected. Sprague-Dawley rats (n = 10) were studied using free-flow micropuncture techniques during euvolemia and following acute ipsilateral denervation. Glomerular filtration rate and single nephron glomerular filtration rate were stable. Absolute proximal bicarbonate reabsorption fell following denervation (933 +/- 40 to 817 +/- 30 pmol/min) with a parallel reduction in chloride reabsorption (1,643 +/- 116 to 1,341 +/- 129 peq/min). Urinary sodium, potassium, bicarbonate, and chloride excretion all increased significantly. To further assess the physiological significance of neurogenic modulation of proximal transport, other rats (n = 6) were subjected to acute unilateral nephrectomy (AUN). There is evidence that AUN induces a contralateral natriuresis (renorenal reflex) at least partially by causing inhibition of efferent renal nerve traffic. AUN caused significant changes in proximal NaHCO3 and NaCl reabsorption as well as in whole kidney electrolyte excretion in the same pattern as had denervation. Prior denervation of the remaining kidney prevented the proximal and whole kidney response to AUN (n = 6). In conclusion, depression of renal nerve activity inhibits both NaHCO3 and NaCl reabsorption in the rat superficial proximal convoluted tubule. The data are consistent with the hypothesis that changes in renal nerve activity modify whole kidney electrolyte excretion under physiological conditions at least partially by regulating proximal transport.

Increased tubuloglomerular feedback activity in Milan hypertensive rats

1986 ◽  
Vol 250 (6) ◽  
pp. F967-F974 ◽  
Author(s):  
U. Boberg ◽  
A. E. Persson
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Tubuloglomerular Feedback ◽  
Spontaneously Hypertensive ◽  
Arterial Blood ◽  
Single Nephron ◽  
Flow Pressure ◽  
Normotensive Strain

Studies of whole-kidney function and micropuncture measurements in superficial nephrons were performed to investigate the role of the tubuloglomerular feedback (TGF) in the excretion of salt and water in hydropenic and volume-expanded rats of the spontaneously hypertensive Milan strain (MHS). The rats were 3.5-5 and 5-7 wk old, and age-matched animals from the Milan normotensive strain (MNS) served as controls. There was no difference in mean arterial blood pressure (Pa) between the 3.5- to 5-wk-old prehypertensive MHS (MHSp) and MNS rats, but the glomerular filtration rate (GFR) was higher in MHSp than in MNS [1.35 vs. 0.80 ml X min-1 X g kidney wt (KW)-1, P less than 0.01]. The distal single-nephron glomerular filtration rate (SNGFR) was also higher in MHSp than in MNS (28.6 vs. 20.2 nl X min-1 X g KW-1, P less than 0.05). TGF was determined from both stop-flow pressure response and proximal and distal SNGFR. It was found that MHSp exhibited essentially no TGF response. During development of hypertension 5- to 7-wk-old MHS (MHSd) had a higher Pa than MNS (120 vs. 98 mmHg, P less than 0.01). Normally GFR and SNGFR increase with age, and such was the case with MNS (0.8 to 1.02 ml X min-1 X g KW-1 and 20.2 to 23.4 nl X min-1 X g KW-1), but in MHSd there was a decrease in both GFR and SNGFR with age (1.35 to 1.10 ml X min-1 X g KW-1 and 28.3 to 18.3 nl X min-1 X g KW-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased single-nephron protein excretion after renal ablation in nephrotic rats

1988 ◽  
Vol 255 (6) ◽  
pp. F1243-F1248 ◽  
Author(s):  
T. W. Meyer ◽  
H. G. Rennke
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Hydraulic Pressure ◽  
Nephron Number ◽  
Renal Ablation ◽  
Single Nephron ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

The effects of reducing nephron number in rats with established nephrosis were investigated. Rats received an injection of adriamycin and were divided into three groups with similar values for proteinuria after 4 wk. Group 1 rats were then subjected to sham operation. Group 2 rats were subjected to four-fifths renal ablation, and group 3 rats were subjected to four-fifths renal ablation and then maintained on enalapril. Micropuncture and morphological studies were performed 3 wk later. During this 3-wk period, proteinuria increased slightly in each group. Increased proteinuria in groups 2 and 3 reflected a dramatic increase in remnant nephron proteinuria after renal ablation in nephrotic rats. Increased remnant nephron proteinuria in groups 2 and 3 was associated with increased single-nephron glomerular filtration rate (group 1, 30 +/- 2 nl/min; group 2, 54 +/- 3 nl/min; group 3, 41 +/- 4 nl/min) and increased glomerular volume (group 1, 0.93 +/- 0.05 x 10(6) micron 3; group 2, 1.30 +/- 0.09 x 10(6) micron 3; group 3, 1.27 +/- 0.05 x 10(6) micron 3). The increase in single-nephron glomerular filtration rate after renal ablation in both group 2 and 3 rats was attributable to an increase in glomerular plasma flow (group 1, 119 +/- 14 nl/min; group 2, 217 +/- 18 nl/min; group 3, 183 +/- 13 nl/min) without a significant increase in glomerular transcapillary hydraulic pressure (group 1, 45 +/- 1 mmHg; group 2, 48 +/- 3 mmHg; group 3, 44 +/- 2 mmHg). Group 2 exhibited an increase in systemic blood pressure that was prevented by enalapril treatment in group 3. These studies show that an increase in remnant nephron proteinuria accompanies glomerular hypertrophy and hyperfiltration when nephron number is reduced in nephrotic rats. This increase in remnant nephron proteinuria is not attributable to elevation of systemic or glomerular capillary pressure.

Feedback mediation of SNGFR autoregulation in hydropenic and DOCA- and salt-loaded rats

1979 ◽  
Vol 237 (1) ◽  
pp. F63-F74 ◽  
Author(s):  
L. C. Moore ◽  
J. Schnermann ◽  
S. Yarimizu
Keyword(s):  
Glomerular Filtration Rate ◽  
Arterial Pressure ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Tubuloglomerular Feedback ◽  
Single Nephron ◽  
Proximal Tubular

Tubuloglomerular feedback (TGF) mediation of autoregulation was investigated by measuring the response of single nephron glomerular filtration rate (SNGFR) to changes in arterial pressure (AP) following acute or chronic TGF inhibition. In hydropenic rats with intact TGF, distal SNGFR was 25.0 +/- 1.2 (SE) and 23.9 +/- 1.4 nl/min at AP of 111 and 135 mmHg, respectively. In the same 20 nephrons during proximal tubular microinfusion of furosemide, distal SNGFR was 23.6 +/- 1.4 (n = 16) and 29.7 +/- 1.4 nl/min (n = 20) (P less than 0.001, n = 16) at 112 and 133 mmHg. When determined proximally, SNGFR was 25.6 +/- 1.0 and 29.5 +/- 0.9 nl/min (P less than 0.001, n = 31) at 112 and 157 mmHg; kidney GFR increased similarly. These data and the predictions of a GFR model were then used to estimate autoregulatory efficiency. This analysis indicated that partial autoregulation occurred during TGF inhibition. Therefore, TGF is an essential, but probably not the only, mechanism mediating SNGFR autoregulation.

Effect of synthetic ANP on renal and loop of Henle functions in the young rat

1986 ◽  
Vol 251 (2) ◽  
pp. F220-F225 ◽  
Author(s):  
D. R. Roy
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Wistar Rats ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Urine Volume ◽  
Fold Increase ◽  
Young Female ◽  
Constant Infusion ◽  
Single Nephron

The present studies were undertaken to determine, by recollection micropuncture, the effect of a synthetic atrial natriuretic peptide (ANP) on the absolute and fractional deliveries of water and sodium to the juxtamedullary end-descending limb. Two groups of young female Munich-Wistar rats were studied: control (n = 8) received the vehicle only; and ANP (n = 12) received a prime followed by the constant infusion of a synthetic rat atrial peptide (28 amino acids). With the infusion of ANP, clearance of p-[14C]aminohippurate [( 14C]PAH) and glomerular filtration rate (GFR) fell significantly. Despite this fall in GFR and renal plasma flow, ANP produced a 2-fold increase in urine volume and a 10-fold increase in sodium excretion. Absolute and fractional sodium deliveries to the end-descending limb increased by approximately 30% in the ANP group, whereas mean juxtamedullary single-nephron glomerular filtration rate (SNGFR) remained stable. In three additional rats prepared for micropuncture of the superficial end-accessible proximal tubule, ANP reduced cortical SNGFR by approximately 15%. By contrast, GFR did not decline in response to ANP in larger rats, when treated identically. We conclude that in young rats ANP can produce a natriuresis in the absence of a rise in GFR; the fall in GFR observed following ANP is due presumably to the immaturity of the animals used in these studies; and ANP produces a rise in absolute and fractional water and sodium deliveries to the end-descending limb that cannot be attributed to a change in SNGFR.(ABSTRACT TRUNCATED AT 250 WORDS)

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