
inhibition by actinomycin d of bone resorption
induced by parathyroid hormone or vitamin a.
actinomycin d inhibits cell proliferation in
control cultures of embryonic rat bone
and prevents the stimulation of bone resorption
by parathyroid horome (pth) or vit.
a.  with a dose of 0.004 /ml. of actinomycin
d, pth effects are only partially inhibited
and this inhibition can be overcome
by increasing the dose of pth.  these
findings suggest that these agents act competitively.
