A role for parathyroid hormone in the mechanical responsiveness of
rat bone.
Chow, J. W. M., S. Fox, C. J. Jagger, and T. J. Chambers.
Department of Histopathology, St George's Hospital Medical School,
London SW17 ORE, UK
APStracts 4:0217E, 1997.
We investigated the relationship between parathyroid hormone (PTH) and
and mechanical stimulation in mechanically-induced osteogenesis. In
normal rats, mechanical stimulation of the 8th caudal vertebra
induced an osteogenic response. This was augmented by a single
injection of human PTH (1-34) 30-45 mins prior to loading. No
osteogenic response was seen in thyroparathyroidectomized (TPTX)
rats; the osteogenic response was restored by a single injection of
PTH before stimulation, suggesting that physiological levels of PTH
are necessary for the mechanical responsiveness of bone. c-fos
expression was detected only in the osteocytes of those rats that
were both mechanically stimulated and given PTH. This suggests that
PTH supports mechanically-induced osteogenesis by sensitizing either
the strain-sensing mechanism itself, or early responses of bone to
strain-generated signals. The osteogenic response was not augmented
by two further daily injections of PTH, and was not seen in TPTX rats
in which PTH administration was started 3 days after loading. These
results reveal a major role for PTH in the mechanical responsiveness
of rat bone.
Received 16 June 1997; accepted in final form 24 September 1997.
APS Manuscript Number E283-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 7 October 1997