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Phloretin sensitive active urea absorption in frog skin

M Svelto, V Casavola, G Valenti

Pflugers Archiv : European Journal of Physiology

|September 1, 1982

Summary

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This study shows that frog skin actively absorbs urea, a process influenced by sodium transport and inhibited by phloretin. This active urea absorption mechanism is located on the external side of the skin epithelium.

Area of Science:

Urease activity and transport
Amphibian physiology
Epithelial transport mechanisms

Background:

Urea transport across biological membranes is crucial for nitrogen excretion and homeostasis.
The skin of amphibians, like Rana esculenta, serves as a significant interface for physiological exchange with the environment.

Purpose of the Study:

To investigate the presence and characteristics of active urea absorption in isolated frog skin.
To elucidate the mechanisms and potential coupling of urea transport with other ions.

Main Methods:

Experiments using isolated Rana esculenta skin preparations.
Measurement of urea influx and outflux under varying conditions.
Kinetic analysis (saturation kinetics, Km determination).

Related Experiment Videos

Inhibition studies using uncoupling agents (FCCP) and phloretin.

Main Results:

Evidence for active urea absorption against a concentration gradient.
Urea transport exhibits saturation kinetics with an apparent Km of 1.33 mM.
Inhibition of inward urea transport by external phloretin, suggesting an external epithelial mechanism.
Phloretin also stimulates sodium active transport, hinting at potential urea-sodium coupling.

Conclusions:

Isolated frog skin actively absorbs urea via a phloretin-sensitive mechanism on the external epithelium.
The findings suggest a possible coupling between active urea and sodium transport in Rana esculenta.
This study provides insights into the physiological regulation of urea balance in amphibians.