Quantification of Hemodynamics in Murine Myocardium following Manganese Infusion

This study examines the: (a) temporal stability of cardiac hemodynamic indices in C57BL/6 mice under anesthesia for 90 min.; (b) effects of Mn 2+ on mouse hemodynamic response. Male C57BL/6 mice (n=16, age=10±1 wks, weight=27±1 g) were ventilated with 1.5% isoflurane in 50:50% O 2 /N 2 O, and catheterized using a Millar catheter via the right carotid. Mn 2+ was infused via a left jugular catheter. For quantification of absolute volumes in control mice (n=7), parallel conductance and stroke volume were estimated following a 10% hypertonic saline infusion, and separate aortic flow experiments (n=3). In another cohort of mice (n=6) MnCl 2 was infused (190nmoles/g bw) for 30 min. following 11 min. of baseline recording. Mean systolic and diastolic indices of function during control, baseline, and Mn‐infused periods were [EF(%): 62.1±3.0, 51.5±2.0, 56.6±3.6], [dP/dt max (mmHg/s) 7946±367, 7061±375, 8061±681], [E a (mmHg/μl) 7.5±0.2, 8.2±0.2, 7.6±0.7], [SW (mmHg/μl) 961±36, 850±43, 929±85], [dP/dt min (mmHg/s) −8345±347, −7371±475, −8545±611], [τ glantz (ms) 11.4±0.4, 12.0±0.5, 9.9±0.9]. Mean values during Mn infusion are significantly different at α=1%. Stable temporal hemodynamic responses were achieved in control mice. Positive and negative ionotropy resulted from Mn 2+ infusion, possibly as a result of modulating catecholamine release effects. Grant support: Hellenic Bank, Research Promotion Foundation.