Radioactive metabolic data using

Reduction of Radioactive Metabolic Data Using A Desk-Top Computer Network... 

When using radiolabeled proteins, it is important to show that the radiolabeled test material maintains activity and biological properties equivalent to that of the unlabeled material. Tissue concentrations of radioactivity and/or autoradiography data using radiolabeled proteins may be difficult to interpret due to rapid in vivo metabolism or unstable radiolabeled linkage. Care should be taken in the interpretation of studies using radioactive... 

Toxicokinetics studies are designed to measure the amount and rate of the absorption, distribution, metabolism, and excretion of a xenobiotic. These data are used to construct predictive mathematical models so that the distribution and excretion of other doses can be simulated. Such studies are carried out using radiolabeled compounds to facilitate measurement and total recovery of the administered dose. This can be done entirely in vivo by measuring levels in blood, expired air, feces, and urine these procedures can be done relatively noninvasively and continuously in the same animal. Tissue levels can be measured by sequential killing and analysis of organ levels. It is important to measure not only the compound administered but also its metabolites, because simple radioactivity counting does not differentiate among them. 

While parenteral exposure is not a route posing a significant environmental threat to human health from the isotopes of radium, data acquired in studies using this route are presented here because thousands of persons did acquire radium via this route, and most of the toxicity and metabolic studies with experimental animals have used this route. It is again important to note that effects observed after parenteral administration of radium may be attributed not only to radium itself, but to the presence of any or all of its daughter products and their radioactive emissions in vivo. 

The rice lamina inclination assay is very sensitive to brassinosteroids (11). In the second set of studies, we examined the metabolism of radioactive castasterone in the rice lamina assay (Yokota, T. et. al., unpublished data). The fate of tritiated castasterone was monitored for 72 hr. During incubation, again brassinolide was not detected. However, polar metabolites accumulated and the amount increased during 72 hr. (Figure 7). The polar metabolites seemed not to be changed after hydrolysis using either enzyme, hydrochloric acid or sodium hydroxide. 

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