PKINCIPLES OF TRACER METHODOLOGY 



25 



0.05 



0.04 



0.03 



0.02 



0.01 



A 



Phase 1 

 Plasma 



k^ 0.022 



/I, Phase 2 

 ' Bone 



V Other 

 phases 



A^=0.05 [/-e-^-^^^*) 



1 



40 



80 



1 



200 



240 



120 160 



Time t ,min 



Fig. 1-4. Simple accumulation in one phase. Deposition of Ca^* in rabbit bone. 

 [From R. 0. Thomas, T. A. Litovitz, M. I. Rubin, and C. F. Geschickter, Dynamics of 

 Calcium Metabolism: Time Dislribution of Intravenously Administered Radiocalcium, 

 Am. J. PhijsioL, 169: 568-575 (1952).] 



of the younger animals were able to accumulate about twice as much Ca"** 

 as were those of the older animals. 



Simple Turnover — No Return of Labeled Substance. It is generally 

 recognized that many of the body constituents are continually undergoing 

 simultaneous formation and degradation. These are usually independent 

 processes, and the net change in the concentration of the constituent will 

 depend upon the relative rates of synthesis and degradation. Certainly 



