
effects of parathyroid hormone and other proteins in vitro
on mitochondrial metabolism
it is apparent that in addition to parathyroid hormone, several
non-hormonal basic proteins stimulate mitochondrial respiration, ion
transport, and atpase, but inhibit the 32pi-atp exchange reaction.
thus these effects may not be so uniquely a measure of the biological
actions of parathyroid hormone as the previous reports suggested.
rasmussen et al. (1964) have also isolated from parathyroid
extracts a protein that is inert in vivo but stimulates mitochondrial
transport of phosphate in vitro.  they postulated that this protein
might be yet another biologically important factor produced by para-
thyroid glands.  the latter speculation may not be warranted in view
of the uncertain specificity of protein effects on mitochondria.  all
of our tests completed to date show that the non-hormonal parathyroid
proteins c1 and c2 are unrelated either biologically, immunologically,
or chemically (by amino-acid analysis) to the parathyroid hormone.
further rigorous studies are necessary to precisely determine
whether any effects of parathyroid hormone on mitochondria validly
reflect the mechanism of action of the hormone and whether it is sound
to use the in vitro tests as bioassay tools.
