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

This study determined the effects of nicotine on serum concentrations of several calciotropic hormones, and bone formation and resorption end-points in 7 month old, adult female rats. Animals were administered either saline (n= 9/group), low dose nicotine at 3.0 mg/kg/day (n=10/group) or high dose nicotine at 4.5 mg/kg/day (n=11/group) by subcutaneous osmotic minipumps. At the end of a three months treatment period, serum concentrations of calcium, phosphorus, parathyroid hormone, calcitonin, 25-hydroxyvitamin D and 1,25- dihydroxyvitamin D were determined. Femora, tibiae, and lumbar vertebrae (3- 5) were collected and bone parameters evaluated included mineral density and content (femora and vertebrae), strength (femora and vertebrae) and histomorphometry (tibiae). Animals given nicotine had significantly lower levels of 25-hydroxyvitamin D than controls [20.8±1.4 ng/ml for the low dose group and 20.7±1.0 ng/ml for the high dose group versus 27.6±1.3 ng/ml for the control group (mean±S.E.M.), P2 versus 6.2±0.2 mm², P