Reginald A. Shipley

Carbon Dioxide Stores in the Study of Energy Metabolism

As a tool to study energy metabolism, radiocarbon has been more useful to establish routes than to assess rates. Methodology for the measurement of rates is, indeed, still evolving. The metabolic alterations accompanying fasting, or those responsible for a disorder such as diabetes, are attributable to slowing or acceleration of normal chemical transformations rather than complete loss of any pathway or addition of new ones. In applying the method of compartment analysis to study rates, a persisting challenge has been to devise models of in vivo systems which are not unrealistically complex yet are not oversimplified. Some of the gropings of the past 20 years, aside from their historical interest, will serve to illustrate certain pitfalls and will permit us to get a close look at some of the compromises which have been made. The problem of measuring the conversion rate of glucose carbon to CO2 carbon will serve as a starting point.