Surface electrocardiogram and action potential in mice lacking urea transporter UT-B

Area of Science:

• Cardiology
• Physiology
• Molecular Biology

Background:

• Urea transporter UT-B is expressed in various tissues, including the heart.
• The specific role of UT-B in cardiac function is not well understood.

Purpose of the Study:

• To investigate the cardiac phenotype associated with UT-B deletion in mice.
• To determine the impact of UT-B absence on heart electrophysiology and function.

Main Methods:

• RT-PCR and Western blot to confirm UT-B expression in wild-type and null mice.
• Surface electrocardiogram (ECG) recordings in mice at multiple ages.
• Electrophysiological studies including action potential and sodium current recordings in isolated ventricular myocytes.

Main Results:

• UT-B expression was confirmed in wild-type mouse hearts, absent in null mice.
• UT-B null mice exhibited significantly prolonged P-R intervals and developed age-dependent heart block (Types II and III).
• Cardiac electrophysiology was altered, showing decreased action potential amplitude and Vmax, prolonged action potential duration, and reduced maximal sodium current in UT-B null mice.

Conclusions:

• UT-B deletion in mice results in progressive cardiac conduction defects and heart block.
• These findings highlight a critical role for UT-B in maintaining normal cardiac electrical activity.
• The study provides the first evidence linking UT-B deficiency to cardiac dysfunction and heart block.