
tissue distribution of electrolytes, ca and mg in experimental
hyper- and hypoparathyroidism.
the effects of experimental hyper- and
hypoparathyroidism on plasma and tissue
distribution of electrolytes and tissue
exchangeability with ca and mg were studied
in dogs following acute renal pedicle
ligation.  in hyperparathyroidism, plasma concentrations
of mg and inorganic p as
well as ca were increased.  a greater accumulation
of ca occurred in some tissues
and a lesser accumulation in others than
in acute hypercalcemia of comparable
severity and the fractional rate of exchange
of tissue ca was 30% more rapid than
in control and acute hypercalcemic dogs.
bone exchange of ca was not significantly
increased.  cell mg concentrations were
not appreciably altered by hyperparathyroidism
except for a significant 9% decrease
in myocardium, but the fractional rate
of exchange of tissue mg was increased.
acidsoluble p concentrations were decreased
in 3 tissues and na and c1 concentrations
were decreased by 10 to 25% in 4 tissues.
in hypoparathyroidism, in addition to a
decreased plasma ca, the increment
in plasma inorganic p that usually occurs
after renal pedicle ligation was 75% less
than in control dogs.  cell ca concentrations
were decreased by 10-40% but the
fractional rate of exchange of tissue ca was
unaltered.  although cell mg concentrations
were unaltered a 40% increase occurred
in the exchangeability of skeletal muscle
mg.  tissue na and c1 concentrations were
decreased by 20% in 2 tissues.  it has been
previously reported that hypercalcemia
increases cell ca concentrations by raising
the extracellular ca concentration gradient.
evidence has also been presented that
hypercalcemia directly inhibits cell
influx of mg and na and cell efflux of k.
with altered parathyroid activity, 2 types
of effects are observed: those which are
dependent upon an abnormal extracellular
ca concentration and those which appear to
be due to intrinsic effects of parathormone
on cell cation transport.  the present
data are compatible with the hypotheses
that parathormone stimulates bidirectional
transport of cell ca and p, stimulates
cell influx of mg and opposes the effects of
hypercalcemia on cell transport of univalent ions.
