Proximal bicarbonate reabsorption during Ringer and albumin infusions in the rat
The Journal of Clinical Investigation
|June 1, 1976
Summary
Extracellular volume expansion suppresses fractional bicarbonate reabsorption in rat kidneys. However, absolute net bicarbonate reabsorption and water reabsorption remain linked, indicating no overall suppression of these key kidney functions.
Area of Science:
- Nephrology
- Physiology
- Renal Physiology
Background:
- Extracellular volume expansion is known to suppress whole kidney bicarbonate reabsorption.
- The single nephron mechanisms underlying this suppression are not well understood.
- Bicarbonate transport's role in proximal tubule fluid efflux is under investigation.
Purpose of the Study:
- To investigate proximal tubular bicarbonate handling in rats during extracellular volume expansion.
- To assess the effects of Ringer and albumin infusions on bicarbonate and water reabsorption at the single nephron level.
Main Methods:
- Recollection micropuncture studies were performed in rats.
- Infusions of modified Ringer or salt-poor hyperoncotic human albumin were administered.
- Measurements were taken under stable arterial PCO2, plasma [HCO3-], and plasma [K+] levels.
Main Results:
- Fractional bicarbonate reabsorption significantly decreased during both Ringer (31%) and albumin (20%) infusions.
- Absolute net bicarbonate reabsorptive rates did not change significantly.
- Strong positive correlations were found between absolute net reabsorption rates of bicarbonate and water.
Conclusions:
- Ringer and albumin infusions do not suppress absolute net bicarbonate reabsorption in rat proximal tubules under free-flow conditions.
- Linked changes in absolute bicarbonate and water fluxes characterize these infusion protocols.
- This suggests a coordinated handling of bicarbonate and water within the proximal tubule during volume expansion.
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