Effects of nicotine on bone mass, turnover, and strength in adult female rats

This study investigated the effects of nicotine, the chemical responsible f or tobacco addiction, on bone and on serum mineral and calcitropic hormone levels in adult, female rats to help resolve a current controversy regardin g the impact of nicotine on bone health, Seven-month-old rats received eith er saline (n = 12), Iow-dose nicotine (4.5 mg/kg/day, n = 2), or high-dose nicotine (6.0 mg/kg/day, n = 12) administered subcutaneously via osmotic mi nipumps for 3 months. Blood, femora, tibiae, and lumbar vertebrae (3-5) wer e collected at necropsy for determination of serum mineral and hormonal con centrations, bone density (femora and vertebrae), bone turnover (tibiae), a nd bone strength (femora). The presence of nicotine in serum (111 +/- 7 and 137 +/- 10 ng/ml for the low- and high-dose nicotine groups, respectively) confirmed successful delivery of the drug via osmotic minipumps. Nicotine- induced treatment differences were not detected in serum calcium, 25-hydrox yvitamin D, and 1,25-dihydroxyvitamin D. However, serum phosphorus and para thyroid hormone (PTH) were higher in rats treated with high-dose nicotine, and serum calcitonin was lower in rats treated with both high- and low-dose nicotine than in control rats. Nicotine treatment had no effect on tibial cancellous or cortical bone turnover or femoral bone mineral content (BMC) and density (BMD). Femoral ultimate load and vertebral BMC were lower in ra ts treated with high-dose, nicotine than in control rats. We conclude that nicotine at serum concentrations 2.5-fold greater than the average in smoke rs has limited detrimental effects on bone in normal, healthy female rats.