Tissues metabolism, proton production

In the electrochemical interpretation of metabolism presented here, we discount the significance of chemical reactions occurring under conditions well removed from equilibrium as important sources of heat production. Rather, we identify those processes associated with electronic and protonic current flow as the critical elements in heat production. The relationship between body surface area and heat production becomes more readily understandable when it is appreciated that these heat-producing processes take place within cellular membranes (or the microtrabecular lattice). Thus, the finding that heat production is a function of body surface area rather than tissue mass may be a macroscopic reflection of the fact that cellular electrochemical reactions occur in two dimensions, in contrast with three-dimensional, scalar chemical reactions. 

The invention of the surface coil and the development of NMR probes containing life-support systems have made it possible to observe high-energy phosphates in intact tissues and whole organisms. P NMR has been used for the safe, noninvasive detection of disease states in tissues without risk to the patient. Metabolic products soluble in the cytoplasm of skeletal muscle, heart, kidney, brain, and eye have all been qualitatively observed and identified. With the appropriate use of standards, determination of relaxation times, and performance of the necessary instrument calibrations, quantitative results can be comparable to those obtained in wet-chemical assays. The protonation/deprotonation equilibrium of phosphates influences the P chemical shift, facilitating the noninvasive determination of tissue pFi. 

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