INHIBITION BY STEROIDS OF PARATHYROID HORMONE-INDUCED Ca⁴⁵ RELEASE FROM EMBRYONIC RAT BONE IN VITRO

¹ Department of Pharmacology, Northwestern University Medical School, Chicago, Illinois

In vitro effects of several steroid hormones and cholesterol on bone resorption were examined in tissue culture. Embryonic rat long bones were prelabeled with Ca⁴⁵. Bone resorption was produced with parathyroid hormone and was quantified as release of Ca⁴⁵ from the paired bones. Steroids were added over a 10^-9 to 10^-3 M concentration range. All of the steroids at the highest concentrations tested (10^-5-10^-3 M) inhibited the response to parathyroid hormone. At these concentrations several steroids also inhibited Ca⁴⁵ release in the absence of parathyroid hormone. At intermediate concentrations (1.5 x 1O^-8 to 10^-6 M), hydrocortisone, corticosterone, testosterone and cholesterol all showed some inhibition. At concentrations less than 1.5 x 10^-8 M, only dexamethasone was inhibitory. The inhibition produced by dexamethasone could be antagonized by increasing the concentration of parathyroid hormone. The results indicate that, at concentrations achieved in vitro, glucocorticoids can inhibit bone resorption by a direct effect on bone. In addition, the results suggest that the in vitro inhibition of bone resorption produced by steroid hormones at high concentrations is a nonspecific effect.

This article has been cited by other articles:

				N. S. Krieger, K. K. Frick, and D. A. Bushinsky Cortisol Inhibits Acid-Induced Bone Resorption In Vitro J. Am. Soc. Nephrol., October 1, 2002; 13(10): 2534 - 2539. [Abstract] [Full Text] [PDF]

				E. O. Abu, A. Horner, V. Kusec, J. T. Triffitt, and J. E. Compston The Localization of the Functional Glucocorticoid Receptor {alpha} in Human Bone J. Clin. Endocrinol. Metab., February 1, 2000; 85(2): 883 - 889. [Abstract] [Full Text]