ISSN:
1432-2013
Schlagwort(e):
Rat
;
Micropuncture
;
Microperfusion
;
Loop of Henle
;
Stop-flow pressure
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Abstract The behavior of the feedback mechanism, that causes glomerular capillary pressure and filtration rate to decrease when tubule fluid flow rate through the loop of Henle of the same nephron is increased, was examined in rats before and during isotonic extracellular fluid volume expansion. The loop of Henle was perfused from the late proximal tubule at either 10 or 40 nl/min while proximal fluid was collected to measure single nephron filtration rate (SNGFR), while proximal stop-flow pressure (PSF) was measured, or while fluid was collected from the early distal tubule to assess reabsorption of fluid and electrolytes by the loop of Henle. During control periods increasing loop perfusion caused SNGFR to decrease 37%, PSF to decrease 19%, and absorption of fluid, sodium and chloride by the loop of Henle to increase. After 1 h of infusion of isotonic NaCl solution the same change in loop flow causes a 19% decrease in SNGFR and an 8% decrease in PSF. Fluid absorption by the loop of Henle did not increase with increased loop perfusion. Increases in Na and Cl absorption were similar to the increases in control periods. The smaller decreases in SNGFR and PSF indicate that acute volume expansion decreases the sensitivity of the feedback response. The mechanism of this decrease in gain could involve interference with local generation or action of angiotensin, or a change in the composition or pressure of interstitial fluid tending to dilate the pre-glomerular resistance vessels.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00582339
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