The effect of glucocorticoids on osteoblast function. The effect of ³

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corticosterone on osteoblast expression of beta 1 integrins. Doherty WJ. DeRome ME. McCarthy MB. Gronowicz GA. J Bone Joint Surg Am. 77(3):396-404, 1995 Mar. Á Prolonged treatment with glucocorticoids is known to produce osteoporosis, which is characterized by a decrease in bone mass. Therefore, we studied the effect of glucocorticoids on the formation of bone and on the Á expression of beta 1 integrins in a mineralizing organ culture of fetal  rat parietal bone. Integrins are a family of integral membrane glycoproteins that mediate the adhesion of cells to extracellular matrix macromolecules and affect the growth and differentiation of cells. In situ hybridization with a 32P-labeled beta 1 integrin cDNA probe was performed on parietal bone, treated with or without 100-nanomolar corticosterone for ninety-six hours, to localize and assess the levels of beta 1 integrin mRNA quantitatively. Corticosterone decreased beta 1 integrin mRNA in the osteoblast layer but not in the periosteum. Northern blot analysis demonstrated a 62 per cent decrease in the levels of beta 1 integrin mRNA in the osteoblast layer of bone that had been stripped of its periosteum. Immunofluorescence microscopy confirmed these results, as they * demonstrated a decrease in the levels of beta 1 integrin protein predominantly in the osteoblast layer. This effect was dependent on the concentration of corticosterone. During ninety-six hours of culture, the Á calcium content and the dry weight of control parietal bone increased 157 per cent and 57 per cent, respectively. However, treatment of these cultures with 100-nanomolar corticosterone inhibited calcification by 24 per cent. The administration of glucocorticoid had no significant effect on the DNA content or dry weight.(ABSTRACT TRUNCATED AT 250 WORDS) *