Technical problems in the micropuncture determination of nephron filtration rate and their functional implications

Schnermann, J.; Davis, John M.; Wunderlich, P; Levine, David Z.; Horster, Michael

doi:10.1007/bf00588002

Cited by 61 publications

(16 citation statements)

References 20 publications

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“…Because no method of assessing the activity of the TG feedback system is entirely without limitations, we employed three different approaches. A frequently cited concern about techniques requiring collection of tubule fluid is that artifactual changes in SNGFR may be introduced by the collection technique through alteration of intratubular pressure (particularly during collections from the proximal tubule) (21). In experiment 1 we attempted to avoid altering pressure in Bowman's space by collecting fluid from the distal end of the proximal tubule and by not applying suction on the collection pipette.…”

Section: Discussionmentioning

confidence: 99%

“…This is done because loop flow and the effects of TG feedback on GFR and tubule fluid flow rate are eliminated by the technique of collecting proximal fluid used in experiment 1. Consequently, the true rate of flow in the proximal tubule may be overestimated by this technique (21 5-nl/min increment from the pump setting first eliciting a decrease in stop-flow pressure was also studied. In this fashion each nephron was studied at a minimum of five pump settings in addition to the baseline setting (2 nl/min).…”

Section: Methodsmentioning

confidence: 99%

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Dietary protein suppresses feedback control of glomerular filtration in rats.

Seney¹,

Wright²

1985

J. Clin. Invest.

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We have examined the possibility that changes in glomerular filtration rate (GFR) after changes in dietary protein intake may depend on altered function of the tubuloglomerular (TG) feedback system. We studied male Sprague-Dawley rats after dietary pretreatment for 9.6±3.6 (SD) d with isocaloric diets containing either 6% or 40% casein. We found that GFR in rats fed the high protein diet was 24-29% higher than in rats fed the low protein diet. Simultaneous measurements of single nephron GFR (SNGFR) in the distal tubule were 6.3 nl/min or 21% higher in the rats fed the high protein diet whereas proximally measured SNGFR was not statistically different in the two groups. The higher distally measured SNGFR of rats receiving the high protein diet was associated with a 4.2 nI/ min or 50% smaller suppression of SNGFR by TG feedback (-4.3 vs. -8.5 nl/min, P < 0.001). Loop perfusion experiments demonstrated that in rats fed the high protein diet the TG feedback mechanism was less sensitive than in rats fed the low protein diet. The TG feedback response in rats fed the low protein diet, as assessed by reductions in stop-flow pressure and SNGFR, was half-maximal at flows of 14-15 nl/min. In contrast, the TG feedback response in rats fed the high protein diet was half-maximal at 22-24 nl/min. Maximal suppression of stop-flow pressure and SNGFR and the slope of the TG feedback response to increasing loop flow rates were not different in the two groups. We conclude that the sensing mechanism of the TG feedback system is rendered less responsive by a high protein intake, and that this change permits GFR to increase.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Dietary protein suppresses feedback control of glomerular filtration in rats.

Seney¹,

Wright²

1985

J. Clin. Invest.

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“…Collections were made under 'controlled suction'. Although controversy exists about the validity of measuring SNGFR by sample collection from the proximal tubule (Davis, Schnermann & Horster, 1972;Knox, Ott, Cuche, Gasser & Haas, 1974;Navar, Burke, Robinson & Clapp, 1974;Schnermann, Davis Wunderlich, Levine & Horster, 1971), it was necessary to use this site for sampling. In the youngest Wistar rats used in these studies (20 days old), there are but a few distal tubules on the surface.…”

Section: Micropuncture Studies and Tubular Measurementsmentioning

confidence: 99%

Developmental changes in nephron number, proximal tubular length and superficial nephron glomerular filtration rate of rats.

Solomon¹

1977

The Journal of Physiology

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“…Recent studies have shown that GFR calculated from distal tubular fluid collections are consistently lower than those calculated from proximal tubular fluid collections in that nephron, when distal tubular sodium concentration are presumably very low due to the proximal oil block (57,58). Others have failed to substantiate these findings (59).…”

Section: Microinjection Studiesmentioning

confidence: 99%

Pathophysiology of Experimental Glomerulonephritis in Rats

Allison¹,

Wilson²,

Gottschalk³

1974

J. Clin. Invest.

158

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A B S T R A C T Micropuncture, clearance, immunofluorescence and light microscopy techniques were used to study kidney structure and single nephron function in rats with autologous immune complex nephritis (AICN), a membranous glomerulonephritis developing over 5 to 20 mo, in the more acute and proliferative glomerular basement membrane (GBM) nephritis and in controls. Both models are known to have clinical counterparts in human disease. Kidney functional abnormalities correlated with the degree of architectural derangement. In both AICN and anti-GBM nephritis filtration fraction fell in direct proportion to the fall in glomerular filtration rate (GFR), renal plasma flow being unchanged. Fractional electrolyte excretion increased as the GFR fell. Despite marked heterogeneity of single nephron filtration rate (SNGFR) (AICN, 5-93 nl/min; anti-GBM, 0-50 nl/min) and of proximal tubular hydrostatic pressure (4-48 mm Hg), each nephron showed almost complete glomerulotubular balance, absolute reabsorption to the late proximal convolution varying directly with filtration rate. In addition SNGFR could be related both to proximal intratubular hydrostatic pressure and to calculated glomerular capillary pressure (Pg), being lowest in those nephrons with the highest intratubular pressure. Nephrons with very high filtration rates did not apparently reach filtration equilibrium. Mean SNGFR was significantly lower in the anti-GBM group, while calculated Pg was the same in both. This probably reflects the acute and diffuse involvement of the anti-GBM lesion with different filtration characteristics from Dr.

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Technical problems in the micropuncture determination of nephron filtration rate and their functional implications

Cited by 61 publications

References 20 publications

Dietary protein suppresses feedback control of glomerular filtration in rats.

Dietary protein suppresses feedback control of glomerular filtration in rats.

Developmental changes in nephron number, proximal tubular length and superficial nephron glomerular filtration rate of rats.

Pathophysiology of Experimental Glomerulonephritis in Rats

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