Heart‐Specific Inducible Inactivation of ClC‐3 Gene Eliminates Native Volume‐Sensitive Outwardly Rectifying Anion Currents (VSOACs) and Results in Cardiac Hypertrophy and Compromised Heart Function

To test the hypothesis that chloride channel ClC‐3 short isoform (sClC‐3) comprises a key component of native volume‐sensitive outwardly rectifying anion channels (VSOACs) in mammalian heart and assess its physiological role in cardiac function, we generated cardiac‐specific inducible ClC‐3 knockout (KO) mice, by breeding ClC‐3c/c mice with tetO‐Cre and á‐MHC(á‐myosin heavy chain)‐tTA animals. These transgenic mice were maintained on a doxycycline diet to preserve ClC‐3 expression in the heart. Removal of doxycycline activates Cre recombinase to inactivate the ClC‐3 gene. Examination of VSOACs in isolated KO atrial myocytes 3 weeks off doxycycline revealed a complete elimination of the currents, whereas at 1.5 weeks, the VSOACs were significantly reduced, compared to age‐matched control animals. RT‐PCR from KO atrial myocytes confirmed loss of ClC‐3. Echocardiography revealed dramatically reduced ejection fraction and fractional shortening, and severe signs of myocardial hypertrophy and heart failure in the KO mice at the same time point. The results indicate that sClC‐3 is a key component of native VSOACs and plays a significant cardioprotective role against cardiac hypertrophy and failure.(NIH grants HL‐49254, HL‐063914, and NCRR P20RR1581)