Short-term effects of nicotine on bone and calciotropic hormones in adult female rats

This study assessed the effects of two months nicotine treatment on bone formation and resorption end-points in adult, female rats. In addition, the concentrations of calciotropic hormones which included parathyroid hormone, calcitonin, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D in rats (7 months old) were determined. All animals received either saline (n=7/group), nicotine (3.0 mg/kg/day) (n=7/group) or nicotine (4.5 mg/kg/day) (n=7/group) via subcutaneous implantation of osmotic minipumps containing either saline or nicotine for a period of two months. Serum, right tibia, left femur and lumbar vertebra (3-5) were collected for determination of hormonal concentrations as well as various parameters, including histomorphometry, bone mineral density, bone mineral content and vertebral strength. Although nicotine-treated rats showed a lower level of 25-hydroxyvitamin D [54.4±3.1 ng/ml for the 3.0 mg/kg/day and 55.8±2.8 for the 4.5 mg/kg/day group] (mean±S.E.M.) as compared to controls (74.8±2.8 ng/ml) (P<0.01, Newman- Keuls test), no significant difference could be detected for the levels of the remaining hormones. Similarly, no statistical differences were detected on histomorphometric end-points, bone mineral density, bone mineral content and vertebral strength of rats. We conclude that, in spite of lowering serum 25-hydroxyvitamin D by about 30%, nicotine administration of two months duration does not alter bone mass, strength or formation and resorption end- points.