SELECTIVE LOADING OF RHOD-2 INTO MITOCHONDRIA SHOWS MITOCHONDRIAL CA2-RABBIT CARDIAC MYOCYTES( TRANSIENTS DURING THE CONTRACTILE CYCLE IN ADULT)

A strategy of cold loading of the Ca2+-indicating fluorophore Rhod 2-A M followed by warm incubation was developed to selectively label mitoc hondria of adult rabbit cardiac myocytes. After electrical stimulation , mitochondrial Rhod 2 fluorescence observed by confocal microscopy in creased and then rapidly decayed to baseline. In regions between mitoc hondria, the fluorescent transients were small or absent. Subsequent a ddition of calcium ionophore increased mitochondrial but not cytosolic fluorescence, confirming the mitochondrial localization of Rhod 2. Th ese experiments directly demonstrate rapid mitochondrial free Ca2+ tra nsients during the contractile cycle in rabbit cardiac myocytes. (C) 1 997 Academic Press.