re
COHN ETAL..
72
quantification of the differences in the physiological f
parameters of resorption, slow exchange, and bone turn-:;
over as measured by Ca andSr.
APPENDIX
:
—
Tee
k
feedback is not significant in the first 10 days, but must
occur in the period 10-30 days. It would appear that the
I
fel {o(n))? + op”
function describing this feedback is not a simple ex-
k
ponential function, but is related to the complex nature of
compartment 3 itself. It would be most desirable to
Ty
9
I
» (fF — (ny)?
=
nel
k
4
I
(on)?
9
+
Tp
improve the model with this additional feedback loop
simulating resorption in order to fit not only the 30-day
data but also the longer term Sr data, as well as it now
fits the 10-day data.
The present study demonstrates that while the
absolute values of the parameters obtained with Sr do
differ from those obtained with Ca, the differences are
small and the Sr-derived values do reflect Ca metabolism
quite well in terms of the model derived from the 10-day
om
-—
Y/N —1t
¢, ™ standard deviation of individual values {as determined by
computer)
«.
a, = standard deviation of population
oa, = standard error of sample mean
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ee
Xin
ee ie
¥
© (ay)? + op?
)
“yt+ Eh. SOT Fe tepe ne
im
Fe
Definition of statistical terms in Table 2.
Oy Tt
modes of binding and resorption of the two elements by
bone.
To characterize the resorption or feedback differences
between Sr and Ca, it is necessary to employ the model
in analyzing the long-term (30-day) data. Unfortunately,
atteinpts to fit the 30-day data for both Ca and Sr to
the assumed two-compartment model have been unsuccessful to date. This lack of fit is probably due to the
omission of a feedback from compartments 3 to 1 (p13 =
0) to simulate bone resorption or slow exchange. This
‘
data, With the inclusion of the longer term data, it:
should be possible to improve the model and permit the;.
OR LoSPE eSee me
osseous pools.~ Nevertheless, the higher retention of Sr
from 18 to 30 days indicates a slower turnoverrate of Sr
as compared to Ca, and probably reflects the different
Comparative fixation of calcium and strontium by synthetic
hydroxyapatite. J. Biol. Chem. 235: 2152-2159, 1960.
13. Rosertson, J. S. Theory and use of tracers in determining,
transfer rates in biological systems. Physiol, Rev. 37: 133-154, ~
I
.
t
14. SOACHSON, J., awn H. Leperer. The uptake of Ca‘ and Sr"
by bonein vitro. Arch. Biochem. Biophys. 88: 355-360, 1960.