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.