AJP - Endocrinology and Metabolism, Vol 270, Issue 1 E158-E163, Copyright © 1996 by American Physiological Society
Parathyroid hormone mRNA levels are increased by progestins and vary during rat estrous cycle
E. Epstein, J. Silver, G. Almogi, N. Livni and T. Naveh-Many
Minerva Center for Calcium and Bone Metabolism, Nephrology Services, Hadassah University Hospital, Jerusalem, Israel.
Estrogen increases parathyroid hormone (PTH) mRNA levels in vivo in
ovariectomized rats. We now show that the 19-norprogestin R-5020 given to
weanling rats or mature ovariectomized rats led to a twofold increase in
thyroparathyroid PTH mRNA levels. This increase in PTH mRNA occurred at 24
and 48 h after progesterone but not at 72 h. There were no changes in serum
calcium. In vitro, in primary cultures of bovine parathyroid cells,
progesterone increased PTH mRNA levels threefold at 10(-8) M and twofold at
10(-9) M after 24 h. Progesterone receptor (PR) mRNA was demonstrated in
rat parathyroid tissue by in situ hybridization and in human parathyroid
adenoma by immunohisto-chemistry. Changes in PTH mRNA levels during the rat
estrous cycle were also studied. At proestrus and estrus PTH mRNA levels
were increased significantly by three- and fourfold compared with diestrus.
Our results confirm that the parathyroid gland is a target organ for the
ovarian sex steroids estrogen and progesterone and are of physiological
relevance as shown by the changes during estrus.
