Considerations in Designing and Analyzing Data from Apo-B Turnover Studies
The kinetics of apo-B transport through VLDL, IDL and LDL can be described by models developed from tracer data (1,2). From these models, one obtains estimates of metabolic parameters of interest such as (i) fractional catabolic rates, (ii) production rates, and (iii) transport from one lipoprotein class to another. The models, however, have assumptions built into them which affect the interpretation of the data and parameter estimates. With many new experimental procedures being developed, our knowledge of the structure and function of the plasma lipoproteins is rapidly increasing. Many of these new procedures lend themselves to turnover studies with the result that tracer data of increasing complexity are being generated. These include techniques to subfractionate the traditional lipoprotein populations (3,4) and the utilization of stable as well as radioactive isotopes (5,6). The interpretation of these data means that many of the previously developed models may have to be altered or changed altogether as the assumptions upon which they were based prove no longer to be valid. With tracer studies being used to elucidate altered metabolic pathways in pathophysiological conditions or in response to therapy, one runs a high risk of misinterpreting turnover data using models with underlying false assumptions.
KeywordsEstrogen Radioactive Isotope Progesterone Leucine Triglyceride
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