Sympathetic nervous system as transmitter of mechanical loading in bone.
Sympathetic innervation has been demonstrated in bone. Adrenergic stimulation is one of the transmitters of bone loss by uncoupling between decreased bone formation and increased bone resorption.


OBJECTIVE
By using a non-specific antagonist of -adrenergic pathway (propranolol per os), we hypothesized that we could rescue the uncoupling induced mechanical unloading bone loss in the rat model of tail-suspension.


METHODS
Twenty-two female Wistar rats, 12 week-old, have been divided into three groups: eight tail-suspended rats (SR), six tail-suspended rats treated by propranolol (SRP) and eight non-suspended rats (NSR) during 30 days. Bone mineral density (BMD, g/cm2) has been measured by DXA (Hologic QDR-4500A) at D0 and D30 of the study, in the distal femoral metaphysis (DFM), the femoral diaphysis (FD), the whole body (WB, g) and body composition.


RESULTS
Between D0 and D30, in DFM a significant variation in BMD is observed between NSR and SR (% BMD change: NSR +15.6 +/- 3.1% vs SR -1.0 +/- 1.4%, P < 0.0001) and BMD rescue in SRP group (% BMD change SRP +5.3 +/- 1.5% vs SR -1.0 +/- 1.4%, P = 0.03). In FD, gain of BMD is significant in NSR compared to SR (+17.5 +/- 1.5% vs +8.2 +/- 2.8%, P = 0.007) and to SRP (+17.5 +/- 1.5% vs +10.1 +/- 2.4%, P = 0.046). Gain in SRP group is not significant compared to SR group (P = 0.6). In WB, SRP gain more BMD than NSR (+14.0 +/- 1.8% vs +5.4 +/- 0.7%, P = 0.0002) and than SR (+14.0 +/- 1.8% vs +7.8 +/- 1.4%, P = 0.0043). There is no difference between NSR and SR groups (P = 0.19).


CONCLUSIONS
We demonstrate that -adrenergic pathway of sympathetic nervous system is a major transmitter pathway of mechanical loading in rat bone. A specific study is necessary to analyse a possible systemic effect of propranolol in rat bone. Propranolol could be used to prevent the induced mechanical unloading bone loss as weightlessness
sseur
Régis
R
Service de Rhematologie, CHU Cote de Nacre, Cannes, France.levasseur-r@chu-caen.fr
Sabatier
Jean-Paul
JP
Potrel-Burgot
Céline
C
Lecoq
Bertrand
B
Creveuil
Christian
C
Marcelli
Christian
C
D015502:Absorptiometry, Photon; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000187:drug effects / Q000502:physiology; D001862:Bone Resorption / Q000503:physiopathology*; D001842:Bone and Bones / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D005260:Female; D023421:Models, Animal; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000502:physiology*
D000319:Adrenergic beta-Antagonists; D011433:Propranolol