AJP - Cell Physiology, Vol 270, Issue 4 C1088-C1095, Copyright © 1996 by American Physiological Society
Evidence for receptor-mediated mineralocorticoid action in rat osteoblastic cells
M. K. Agarwal, F. Mirshahi, M. Mirshahi, S. Bracq, J. Chentoufi, M. Hott, A. Jullienne and P. J. Marie
Hormone Laboratory, Institut National de la Sante et de la Recherche Medicale Unite 86, Centre Universitaire des Cordeliers, Paris, France.
Aldosterone significantly enhanced the proliferation of osteoblastic cells
from rat calvaria, and this effect was inhibited by RU 26752 and ZK 91587,
two antagonists specific to the mineralocorticoid receptor (MCR). In
addition, aldosterone inhibited the activity of alkaline phosphatase, a
marker of the osteoblastic phenotype, and this effect was also reversed by
RU 26752. Cytoplasmic staining of MCR was observed in rat calvaria
osteoblasts incubated with a specific polyclonal antiserum raised against
rat kidney MCR. This anti-MCR immunoglobulin G immunoprecipitated and
macroaggregated the MCR-[3H]RU 26752 complex in osteoblastic cytosol. A
single 98-kDa band was observed when osteoblastic cytosol was analyzed by
Western blotting with anti-MCR serum. The 98-kDa band was also obtained
after autoradiography of irradiated osteoblastic cytosol-[3H]R 5020
complex, and this was abolished in the presence of RU 26752. A p26MR probe,
specific to COOH-terminal end of MCR, hybridized with the predicted product
after amplification of total cell RNA by polymerase chain reaction
technique. Furthermore, hybridization of poly(A)+ mRNA from at calvaria
osteoblastic cells with the p26MR probe revealed a major band of
approximately 4.2 kb. Collectively, our studies demonstrate the existence
of a functional MCR in rat calvaria osteoblasts.
