OBJECTIVETo explore the possible mechanism of the erector spinal muscles in idiopathic scoliosis by comparing the expression and localization of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) of the thoracic erector spinal muscles on convex side and concave side.

METHODSThe patient group comprised 8 females and 2 males who were scheduled for spinal surgery. The apex of scoliotic curve in these patients arose between T6 and T11. The mean age was 14.3 (range 12-17) years, and the mean Cobb angle was 57.7 degrees (range 45 degrees-85 degrees). Muscle biopsies were taken bilaterally during surgery from the superficial multifidus muscle at the apex of the curve between the 6th and 11th thoracic vertebral levels. Part of the tissue was fixed in formalin and stained with hematoxylin and eosin; the remaining tissue was snap frozen and processed for immunohistochemistry and Western blot. Immunocytochemistry for nNOS and iNOS were performed using the EnVision two-step method. Western blot was done with antibodys to nNOS and iNOS. Immunoreactive bands were visualized by enhanced chemiluminescence according to the manufacturer's specifications (Amersham Corp).

RESULTSnNOS protein in the erector spinal muscles was localized at the sarcolemma. Western blot demonstrated that nNOS protein expression in the concave side of erector spinal muscles is more than that in the convex side. A significant decrease in nNOS protein and activity was found on the convex side of erector spinal muscles from idiopathic scoliosis patients; There was a little immunoreactivity to iNOS in erector spinal muscles. There was little difference in iNOS protein expression between both sides of the curve. Western blot detected the same results.

CONCLUSIONThere is a greater expression of nNOS and iNOS on the concave side than on the convex side, suggesting nNOS and iNOS may play a role in the pathogenesis of idiopathic scoliosis.