Is Nitric Oxide a Mediator of the Effects of Low-Intensity Electrical Stimulation on Bone in Ovariectomized Rats?

• Published in: Calcified tissue international 2010-07, Vol.87 (1), p.52-59
• Main Authors: Lirani-Galvão, A. P. R., Lazaretti-Castro, M., Portero-Muzy, N., Bergamaschi, C. T., Silva, O. L., Carvalho, A. B., Delmas, P. D., Chavassieux, P.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - physiology; Biochemistry; Biomedical and Life Sciences; Bone and Bones - metabolism; Bone density; Caspase 3; Cell Biology; Cell growth; Electric currents; Endocrinology; Female; In Situ Nick-End Labeling; Life Sciences; NG-Nitroarginine Methyl Ester - pharmacology; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III - metabolism; Orthopedics; Osteocytes - metabolism; Osteocytes - physiology; Ovariectomy; Rats; Rats, Wistar; Rodents
• ISSN: 0171-967X; 1432-0827
• DOI: 10.1007/s00223-010-9357-0

Low-intensity electrical stimulation (LIES) may counteract the effects of ovariectomy (OVX) on nitric oxide synthase (NOS) expression, osteocyte viability, bone structure, and microarchitecture in rats (Lirani-Galvão et al., Calcif Tissue Int 84:502–509, 2009). The aim of the present study was to investigate if these effects of LIES could be mediated by NO. We analyzed the effects of NO blockage (by l -NAME) in the response to LIES on osteocyte viability, bone structure, and microarchitecture in OVX rats. Sixty rats (200–220 g) were divided into six groups: sham, sham- l -NAME (6 mg/kg/day), OVX, OVX- l -NAME, OVX-LIES, and OVX-LIES- l -NAME. After 12 weeks, rats were killed and tibiae collected for histomorphometric analysis and immunohistochemical detection of endothelial NOS (eNOS), inducible NOS (iNOS), and osteocyte apoptosis (caspase-3 and TUNEL). In the presence of l -NAME, LIES did not counteract the OVX-induced effects on bone volume and trabecular number (as on OVX-LIES). l -NAME blocked the stimulatory effects of LIES on iNOS and eNOS expression of OVX rats. Both l -NAME and LIES decreased osteocyte apoptosis. Our results showed that in OVX rats l -NAME partially blocks the effects of LIES on bone structure, turnover, and expression of iNOS and eNOS, suggesting that NO may be a mediator of some positive effects of LIES on bone.