ber de el ama tee ch baeade aldualar’ ll a ee (51) | Ss > ™ (50) — a V;- “av, =8 o——™ —_— 74 times that of the final rate constant i, then at equilibrium their specific activity would be 1% that of the skeleton as a whole. 7. Cortical specific activity at transient ec must be Ve\Y (4) = 1.248, a; tye ; where \; = — = the rate of apposition-resorption for t compartment7. 4. Nowif \; refers to trabecular bone, we can write Ys = Ver _ 8. Substituting the above into (52) and u: and (55) VV (¥e B\ nK 1 (©) = (G), (2). = Leds (=) Tif ox or & assuming + = 0.2 (20% trabecular, 80% cortic g - ~52T' (53) 5. The ratio of S/B, plasma to body specific activities, at transient equilibrium follows from the relations S = Se (54) B= Be™ (55) where i, is the rate constant of cortical bone tion-resorption). 9. For the parameters listed in step 6 1 248 (@ &ca/day ) (365 caye/year)) (1.5 %/year) (1000 gca) oe and the excretion postulate 1 — X/r- dk = 212.6 (56) 1a = OS: Radium in man| A/rAe = 0.995 i where gR/c = B. Then the ratio of the body’s final exponential \ to position-resorption rate in cortical bone. 10. Therefore, Acortex iS Within 1/2% of d fi the two can be equated withoutsignificant error so 11. In general S AC - 6) ~ ak (58) which is the ratio of plasma to bodyspecific activities at final transient equilibrium. 6. Therefore, Vr\ (1 — 7) For caleium, with _ (Vr\ (S\ _ (Xe (@).- (4). @).- a). For y In 17 7 | # (4) X = 1.5%/year c = (59) nk = 0.3 go./day A = 15%/year © = 1000 gee 1000 Soa r= 0.2 nk = 7 gca/day (70 liters/day) eg =4 o=4 for radium in man Vr) no ~ = 0.886 (11 % difference). (Fr) = 0.0078. In other words, if trabeculae have a turnover rate of 4 Even 11%1s still negligible in view of our unce? about A. i's pat 3 iF