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