Dobutamine-induced stress affects intracellular uptake of manganese: a quantitative magnetic resonance imaging study in pigs.

PURPOSE: To determine whether there are differences in increase in longitudinal relaxation rate (delta R1) in the myocardium between bolus administration of Mn2+ ions during rest and during dobutamine-induced stress and, additionally, to determine whether there are differences in delta R1 between bolus injection and infusion of Mn2+ ions during dobutamine-induced stress.
MATERIALS AND METHODS: Pigs were divided into three groups with six pigs in each group. All animals received 15 micromol MnCl2/kg of body weight (b.w.) intravenously either as a bolus injection (groups 1 and 2) or as an infusion over one minute (group 3). The animals in groups 2 and 3 were subjected to dobutamine stress before injection of MnCl2, while those in group 1 were not given dobutamine. T1 was quantified in the myocardium and left ventricular blood pool before contrast injection and repeatedly during a one-hour postinjection period.
RESULTS: A significant difference in delta R1 between the groups with and the group without dobutamine stress was noted in the myocardium up to 45 minutes after contrast agent injection. No such significant difference was found between pigs that received the contrast agent as a bolus injection compared to infusion.
CONCLUSION: Dobutamine stress increases uptake of manganese ions in the myocardium. This increase was independent of whether the contrast agent was administered as a bolus injection or as an infusion. Copyright 2005 Wiley-Liss, Inc.