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Kidney function of the American eel Anguilla rostrata
The American Journal of Physiology
|February 1, 1975
Summary
Eel kidney function differs between freshwater and seawater. Seawater eels exhibit higher urine concentrations, and evidence suggests tubular fluid secretion in both environments, impacting osmoregulation.
Area of Science:
- Comparative physiology
- Renal physiology
- Eel osmoregulation
Background:
- Eels (Anguillidae) exhibit remarkable osmoregulatory plasticity, adapting to both freshwater (FW) and seawater (SW) environments.
- Understanding kidney function is crucial for elucidating how eels maintain fluid and ion balance across different salinities.
Purpose of the Study:
- To investigate urine formation and kidney function in eels acclimated to FW and SW.
- To determine the glomerular filtration rate (GFR) and urine flow rate in eels under different salinity conditions.
- To explore the mechanisms underlying apparent tubular fluid secretion in eel kidneys.
Main Methods:
- Measurement of plasma and urine osmotic and ionic concentrations in FW and SW eels.
- Determination of glomerular filtration rate (GFR) using polyethylene-1,2-glycol-14C (PEG-14C) clearance.
- Assessment of urine flow rate and urinary solute excretion.
- Administration of furosemide to evaluate its effect on Na reabsorption and fluid secretion.
Main Results:
- SW eels had higher plasma and urine osmotic and ionic concentrations than FW eels.
- GFR did not differ between SW and FW eels, but urine flow rate was lower in SW eels.
- Data were consistent with tubular fluid secretion, particularly in FW eels, and inconsistent with GFR underestimation.
- Furosemide induced diuresis by inhibiting Na reabsorption but did not affect apparent tubular fluid secretion.
Conclusions:
- Eel kidney function is significantly influenced by environmental salinity, with SW eels showing adaptations for ion conservation.
- Evidence supports the occurrence of tubular fluid secretion in eel kidneys, contributing to urine formation.
- While ion secretion's role as a driving force for fluid secretion remains unclear, proximal tubular ion secretion followed by distal reabsorption is a possibility.