Comparing isoflurane with tribromoethanol anesthesia for echocardiographic phenotyping of transgenic mice

Cardiac phenotyping of transgenic mice typically requires anesthesia. Chemical-grade tribromoethanol (TBE) is commonly used for this purpose due to its relatively short duration of action, modest cardiodepressive effects, and its noncontrolled status. In the present study, we used both genders of C57BL/6;C3H-Tg(Slc8a1)hKdp transgenic (TG) mice and C57BL/6;C3H wild-type (WT) mice to evaluate isoflurane (ISF) as a pharmaceutical-grade alternative to TBE for echocardiography and electrocardiography. Baseline target physiologic heart rates (beats per minute) were established by use of telemetry as 544 +/- 10 in WT mice and 580 +/- 21 in TG mice. TG and WT animals were anesthetized with either 0.8% to 1% inhalational ISF or 250 mg/kg intraperitoneal TBE. The following parameters were measured or calculated according to the previously defined physiologic heart rates: end diastolic and systolic dimensions; posterior wall and ventricular septal thicknesses; left ventricular mass, aortic ejection times; left ventricular fractional shortening; velocity of circumferential fiber shortening; and left ventricular ejection fraction. No significant difference between anesthetics was found for any measured cardiac parameters. However, the time required for data acquisition was significantly shorter for ISF (10 min) than for TBE (14 min). This study demonstrates that comparable echocardiographic results can be obtained at higher throughput by use of pharmaceuticalgrade ISF than with chemical-grade TBE.