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Progressive heart block and ventricular hypertrophy in mice lacking urea transporter UT‐B

Urea transporters B(UT‐B) is membrane proteins that facilitate urea movement across biological membranes, expressed in kidney, erythrocytes, heart, etc. The aim of this study was to determine the phenotype of UT‐B deletion in heart. UT‐B expression in heart was studied by RT‐PCR and Western blot. Surface electrocardiogram recording (lead II) was measured in wildtype mice and UT‐B null mice. Cardiac function was evaluated by echocardiography, left ventricle internal diameters and wall thicknesses were measured at end systole and end diastole (LVPW(d) and LVPW(s)). RT‐PCR and Western blot analysis showed that UT‐B was expressed in heart in wild‐type mice. No UT‐B transcript and protein was found in UT‐B null mice. ECG recording showed that P‐R interval was significantly delayed in UT‐B null mice vs wildtype mice (p < 0.05). Atrial ventricular heart block type and only appeared in 52 weeks old UT‐B null mice. Echocardiography revealed that the LVPW(d) and LVPW(s) in 52 weeks old UT‐B null mice (1.1128 ± 0.0981 and 1.6157 ± 0.1322 mm) were greatly thicker than age matched wild‐type mice (0.8914 ± 0.1433 and 1.2500 ± 0.1786, P < 0.05 respectively). These results provide the first evidence that UT‐B deletion cause progressive heart block in mice and ventricular hypertrophy is involved in the pathogenesis of heart block. *This study was supported by grant 30670852 from the Natural Science Foundation of China.