AJP - Endocrinology and Metabolism, Vol 270, Issue 6 E955-E960, Copyright © 1996 by American Physiological Society

ARTICLES

Nitric oxide is an early mediator of the increase in bone formation by mechanical stimulation

S. W. Fox, T. J. Chambers and J. W. Chow
Department of Histopathology, St. George's Hospital Medical School, London, United Kingdom.

We tested the ability of NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthase (NOS), to suppress the osteogenic response in a recently developed model of mechanically induced osteogenesis. L-NMMA was given either as a single intraperitoneal dose, 15 min before the episode of mechanical stimulation, or as four doses every 6 h, commencing 2 h after loading. Administration of L-NMMA before loading completely prevented the increase in cancellous bone formation by mechanical stimulation. This suppression was largely lost when L-NMMA was administered after loading. Thus the response is likely to be due to activation of a preexistent constitutive NOS in bone cells during or very soon after mechanical stimulation. Suppression of the osteogenic response by L-NMMA was prevented by coadministration of L-arginine but not by the inactive isomer, D-arginine. These changes in cancellous bone were mirrored by similar changes on the corticoendosteal and periosteal bone surfaces. These data suggest that early release of NO is a key signal in the transduction of mechanical stimuli into subsequent bone formation.

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