Effects Of Implanted Metal Containing Nickel On Pregnancy, Embryogenesis And Carcinogenesis In Female Rats

Objective: The toxicity effects of implanted metal of pure nickel and NiTi alloy used in clinical treatment on pregnancy, embryogenesis and carcinogenesis was investigated. The biological safety of NiTi allay widely used in clinic practice was evaluated via bio-metabolic analysis.Methods: The metal of 99% Nickel (5 g/kg, n=15) and 50% nickel in NiTi alloy (10 g/kg, n=15) were respectively implanted into one side hind limb contacting with thighbone in young Wistar female rats (75～80 day, 180～200 g). Amphimixis was performed after 14 day, and the pregnancy and embryogenesis were sequentially studied. The carcinogenesis of metal containing different of content of nickel was revealed by pathological methods. The concentration of Ni²⁺ in blood, urine, amniotic fluid, milk, placenta and fetus were measured by atomic absorption photometer.Results: The ratio of embryogenesis and nativity was decreased significantly in nickel implanted rats (P<0.05) than that in nickel alloy and sham operated rats (n=15). The weight coefficient of heart, lung or kidney of fetus was declined respectively in nickel implanted rats (P<0.05) than that in nickel alloy and sham operated rats. The body weights of neonatal rats of alloy and sham operated groups were heavier than those of nickel group (P<0.05). After nickel implantation on the 40^th day, an envelope was covered implanted metal of nickel as granulation tissue (diameter: 0.5-1 cm), however, alloy was just covered by a thin layer of fibrous connective tissue. On the 80^th day, a capsular space (diameter: 3-5 cm) was formed, in which was filled with fluid containing many blood cells. The capsular wall was dropsical muscle without any sign of carcinogenesis, but the envelope of alloy was not changed with conspicuous pathology. On the 160^th day, the envelope of implanted metal of nickel was more larger than that on the 80^th day (diameter: 6-7 cm), and the tissues of capsular wall were transformed into sarcoma, in which the fluid was filled with a great deal of mesothelial cells and a few of sarcomatous cells, the sarcomagenic cells were transplanted simultaneously to lung, the tissue type of the focus of infection in lung was the same as the type of bladder. The viability of neonatal rat declined in nickel implanted group, but there was not creditable evidence to show that Ni²⁺ which rusting from the Ni-Ti alloy could result in these effects above.Conclusion: Pure nickel implanted into body caused toxic effect to reduce the ratio of embryogenesis, nativity of female rat, and organ weight coefficient of fetus and body weight of neonatal rat. The Ni rusting from the nickel could lead to sarcoma formation, but the alloy had no such effects. However, nickel alloy used in clinical treatment does not exhibit the same toxic effects in this study, but the results of this study showed that the NiTi alloy may be has the potential toxicity in some unusual physiological condition, and it may have potential damage to human body.