Nicotine does not reduce blood flow to healthy bone in rats

Given the increased incidence of orthopedic complications among smokers, we tested the null hypothesis that nicotine, the most vasoactive substance in cigarettes, does not reduce blood flow to long bones. Nicotine was administered to adult rats at a rate of 2.4 or 3.6 mg/kg/d for 2 weeks to determine if nicotine has a dose-dependent effect on bone blood flow. Control rats received nicotine-free solution. After 2 weeks, the rats were anesthetized. The microsphere technique was used to measure flow to femurs and tibias. Blood was collected to measure plasma nicotine. The lower dose established a plasma level of 14 ng/mL (SEM, 4 ng/mL); the higher dose elevated nicotine to 43 ng/mL (SEM, 11 ng/mL). Neither dose altered blood flow to tibias or femurs. A higher dose or longer treatment may be required to reduce bone blood flow. Alternatively, nicotine may not reduce blood flow to healthy bone at any dose but may delay bone healing by other mechanisms (ie, inhibiting angiogenesis and/or osteogenesis).