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Genesis of the sweat:plasma urea concentration gradient
The Journal of Investigative Dermatology
|April 1, 1976
Summary
Urea is stored in the skin's epidermis, turning over slowly. This sequestered urea, concentrated by water evaporation, is the source of excess urea found in human sweat.
Area of Science:
- Dermatology
- Human Physiology
- Biochemistry
Background:
- Urea is a primary nitrogenous waste product in humans.
- The distribution and turnover of urea within the skin are not fully understood.
- Previous studies have not fully elucidated the source of urea in sweat.
Purpose of the Study:
- To investigate the localization and turnover rate of urea within human skin.
- To determine the origin of the excess urea detected in sweat.
- To explore the physiological and clinical significance of epidermal urea sequestration.
Main Methods:
- Experiments utilized 14C-labeled urea in human volunteers.
- Tracer studies were conducted to track urea distribution and metabolism.
- Skin biopsies and sweat analysis were performed to quantify urea levels.
Main Results:
- 14C-labeled urea was found to be sequestered within the epidermis.
- Urea turnover in the epidermis was significantly slower compared to general body water.
- Insensible water evaporation was identified as a mechanism for urea concentration in the skin.
Conclusions:
- A distinct urea pool exists in the epidermis, separate from systemic circulation.
- This epidermal urea pool serves as the source for the elevated urea concentrations observed in sweat.
- The findings have implications for understanding skin barrier function and urea excretion pathways.