Seasonal changes in mucosal structure and function in ground squirrel intestine.

Area of Science:

• Physiology
• Gastroenterology
• Comparative Biology

Background:

• Seasonal variations impact mammalian physiology, particularly during hibernation.
• The jejunal mucosa's structure and function may undergo significant changes between active and hibernating states.

Purpose of the Study:

• To investigate seasonal alterations in the structure and transport function of the ground squirrel jejunum.
• To determine if enhanced absorptive capacity exists in hibernating animals to compensate for mucosal atrophy.

Main Methods:

• Examined mucosal wet weight, protein content, villus height, and surface area in active and hibernating ground squirrels across seasons.
• Measured transepithelial electrical parameters and nutrient (Na+, 3-OMG) absorption using flux chambers at different temperatures (7°C and 37°C).
• Assessed changes in short-circuit current in response to glucose and alanine.

Main Results:

• Hibernating squirrels had the lowest mucosal mass and surface area, which increased in spring and peaked in summer.
• Nutrient absorption was reduced at 7°C but normalized at 37°C.
• Area-specific absorption (per mucosal area) was highest in hibernators, suggesting enhanced function despite atrophy.
• Stimulated absorptive currents were greater in hibernators compared to fall squirrels.

Conclusions:

• Ground squirrels display significant seasonal variations in jejunal mucosal structure and function.
• Enhanced area-specific nutrient absorption in hibernating squirrels at physiological temperatures may be a compensatory mechanism for mucosal atrophy.
• These findings highlight the adaptive plasticity of the gastrointestinal tract in response to seasonal challenges.