Lung ventilation contributes to vertical lymph movement in anurans

Area of Science:

• Amphibian physiology
• Cardiovascular system
• Lymphatic system

Background:

• Anurans produce lymphatic fluid at high rates due to "leaky" vasculature and high interstitial compliance.
• Lymph is pumped to the venous system by dorsal lymph hearts.
• Mechanisms for moving lymph to lymph hearts, especially against gravity, are not fully understood.

Purpose of the Study:

• To test the hypothesis that lung ventilation influences lymph sac pressure and contributes to vertical lymph movement in anurans.
• To investigate the role of pulmonary ventilation in lymphatic fluid transport and blood volume regulation.

Main Methods:

• Measuring lymph sac pressures (dorsal, lateral, subvertebral) during artificial lung inflation/deflation in anesthetized cane toads (Chaunus marinus) and bullfrogs (Lithobates catesbeiana).
• Simultaneously measuring subvertebral, brachial, and pubic sac pressures during natural ventilation in freely behaving animals.
• Analyzing the relationship between lung pressure and lymph sac pressures.

Main Results:

• Significant correlations were found between lung pressure and lymph sac pressures, indicating pulmonary pressure transmission to surrounding lymph sacs.
• Lymph sac pressures were communicated to the brachial lymph sac during expiration (lung deflation).
• Pressure changes during expiration were sufficient to move lymph vertically towards anterior lymph hearts.

Conclusions:

• Pulmonary ventilation plays a crucial role in lymphatic fluid movement in anurans.
• Breathing mechanics contribute to lymph transport, aiding in blood volume regulation.
• Lymph movement is likely facilitated by pressure changes during the expiratory phase of ventilation.