FIGURE 4.

Metabolic homeostasis is response to electrical stimulus. (A) Mitochondrial Ca²⁺, (B) FADH₂ and (C) NADH concentrations and (D) oxygen consumption in response to electrical stimulus at frequencies of 1, 2 and 3 Hz. The average experimental results are shown by the dashed line. (E) Experimental results of flavoprotein fluorescence in isolated atrial cells in response to electrical stimulus at frequencies of 1, 2 and 3 Hz (n = 7). To quantify the dynamic range of the oxidized vs. reduced flavoprotein pool, 100 μmol/L 2,4-dinitrophenol (DNP); (maximum flavoprotein fluorescence) and 4 mmol/L NaCN (reduced flavoproteins; minimal fluorescence) were added at the end of the experiment. The results are presented as mean (black line) with standard error (gray area).