English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

BACKGROUNDWe wanted to validate by direct measurements in rat tubules a technique used to calculate segmental volume absorption by each segment of the human nephron.METHODSExperiments were performed on 17 rats during hypertonic Na infusion prior to and after frusemide administration. Tubular samples were taken from early distal and last proximal sites. The rate of filtration of single nephrons (SNGFR) was calculated by the technique of total collection of tubular fluid using labelled inulin as a marker. Reabsorption was computed by the tubular fluid to plasma (TF/P) inulin concentration ratio.RESULTSSNGFR was 50 +/- 4 nl/min at the distal (n = 82), 51 +/- 3 nl/min at the proximal sampling site (n = 112, P > 0.65) during baseline conditions. Percent reabsorptions were 85 +/- 1 and 69 +/- 2% respectively (P < 0.0001). During frusemide these values were 52 +/- 6 nl/min and 76 +/- 2% at the distal, 49 +/- 5 nl/min and 66 +/- 2% at the proximal site. In 83 paired proximal collections, fractional (68 +/- 1 versus 67 +/- 1% P > 0.32), absolute reabsorption (34 +/- 2 versus 33 +/- 2, P > 0.50) and SNGFR (50 +/- 2 nl/min versus 50 +/- 3 nl/min, P > 0.99) were not different between baseline and frusemide. In 25 re-collections from the distal tubule these same values were 83 +/- 2% versus 76 +/- 2%, and 48 +/- 4 nl/min versus 55 +/- 6 nl/min respectively. Very similar results were obtained in 55 paired distal-proximal collections during baseline and 42 such pairs during frusemide. In the presence of the diuretic the fractional urine excretion was significantly correlated (R = 0.83, P < 0.0001) with fractional proximal delivery, Na+ resorption by Henle's loop was 22 +/- 2% calculated from clearance data and 23 +/- 1% of GFR from micropuncture data respectively. They were not significantly different (P > 0.70) and were significantly correlated (R = 0.57, P < 0.02).CONCLUSIONSThese data demonstrate that frusemide does not act proximally and that delivery beyond the proximal tubule approximates urine flow rate during the action of the drug. The values of segmental reabsorption along the nephron computed on clearance measurements are superimposable upon those obtained directly by micropuncture.

Segmental reabsorption measured by micropuncture and clearance methods during hypertonic sodium infusion in the rat