Age-related decreases in stimulatory g-protein coupled adenylate
cyclase activity in osteoblastic cells.
Donahue, H. J., Z. Zhou, Z. Li, and L. K. McCauley.
Musculoskeletal Research Laboratory, Department of Orthopaedics and
Rehabilitation, and Cellular and Molecular Physiology, The
Pennsylvania State University College of Medicine, P.O. Box 850, 500
University Drive, Hershey, PA 17033-0850, University of Michigan,
School of Dentistry, Dept PPG, 1011 North University Avenue, Ann
Arbor, MI 48109-1078
APStracts 4:0148E, 1997.
In this study we examined parathyroid hormone (PTH), forskolin (FSK),
and choleratoxin (CTX)-stimulated cAMP accumulation in rat
osteoblastic cells (ROB) isolated from young (4 months), mature (12
months), and old (24-28 months) male rats. Exposure to PTH increased
cAMP accumulation in a concentration-dependent manner in all ROB
cells examined. However, the maximum response in ROB from young rats
was 3 fold greater than the maximal response in those from mature and
old rats. Exposure to FSK also stimulated cAMP accumulation in a
concentration-dependent manner but there were no significant
differences in responsiveness among ROB isolated from young, mature
and old rats. Exposure to CTX resulted in a dramatic concentration
-dependent increase in cAMP in ROB from young rats but only a modest
increase in ROB from mature and old rats. PTH binding kinetics were
similar in ROB from rats in each age group. These data suggest an
age-related defect in stimulatory G-protein coupling to adenylate
cyclase which contributes to decreased osteoblastic responsiveness to
PTH.
Received 15 May 1997; accepted in final form 3 July 1997.
APS Manuscript Number E222-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 24 July 1997