Chapter 24 Subcellular Heterogeneity of Energy Metabolism and KATP Current Oscillation in Cardiac Myocytes

Publisher Summary Modern molecular techniques have given biologist the opportunity to deconstruct the most complicated systems of the cell into component proteins that can be studied with unprecedented biophysical detail. A well-studied biochemical system that has spurred theoretical consideration of periodic phenomena in biological systems is the oscillation of energy metabolism in yeast. Oscillations in energy metabolism occur in cardiac myocytes deprived of exogenous substrates. The oscillations could be detected by following changes in the fluorescence of cellular NADH (reduced form of nicotinamide adenine dinucleotide). Periods of suppressed energy metabolism were indicated by oxidation of NADH and were closely associated with activation of adenosine triphosphate (ATP)-sensitive K + (K ATP ) currents in the cardiac sarcolemma. A dependence on the external glucose concentration suggested that glycolytic oscillations, known to occur in cardiac cytoplasmic extracts, could be involved in the phenomenon. In addition to the oscillations in K ATP current and excitation-contraction coupling, it was clear that mitochondrial function also oscillated under these conditions, because the NADH signal arises primarily from the mitochondrial matrix.