
aspects of circadian periodic changes in
phosphorus metabolism in mice
kinetic studies on the p32 content of
mouse brain phosphorus fractions following
the intraperitoneal injection of p32-labeled
orthophosphate were performed during
two selected segments of the 24-hour time scale.
the results of these studies suggest
that the circadian periodicity in relative
specific activity of brain phospholipids
is probably a consequence of a variation in the extent
of p32 incorporation into brain
inorganic phosphate and is not indicative
of a periodicity in the rate of intermediary
phospholipid metabolism.  data on the postinjection
time course of the specific activities
of plasma inorganic phosphate, liver inorganic phosphate,
and liver phospholipid
suggest a similar explanation for
the circadian periodic changes in relative
specific activity of liver phospholipids.
a circadian rhythm of inorganic phosphate
concentration in mouse plasma is demonstrated.
consideration of a mathematical
model suggests that the observed within-day
variation in p32 distribution and the
circadian periodicity of phospholipid relative
specific activity in liver and brain
are a consequence of this periodicity in
plasma phosphate content.  a significant
within-day variation in total phosphorus
content of liver was observed.  the disturbance
of mice incident to p32 injection
has a marked effect on the plasma content
of inorganic phosphate and corticosterone.
