Release of calcium from bone in vitro by homogenates of embryonic chick parathyroid glands.

Parathyroid glands were removed from chick embryos of 12 to 20 days of development and tested for their ability to stimulate calcium release from calcium-45-labeled embryonic chick bone in organ culture. All glands stimulated calcium-45 release to approximately the same degree, although the glands of 16- and 20-day embryos had a somewhat enhanced calcium-mobilizing ability. It appears that parathyroid hormone is present in the embryonic chick coincidental with the time of early development of the skeleton and is present in similar quantities throughout the remainder of embryogenesis.