Abstract
In order to study the interaction between the human body and synthesized hydroxyapatite (HAP), human peripheral monocytes (immunocytes derived from fresh venous samples) were cultured in medium containing various concentrations of HAP. Viability, phagocytosis rate, protein synthesis, DNA synthesis, enzyme activity [lactic dehydrogenase (LDH) and acid phosphatase (AcP) ] and surface antigens [Leu-15 (CD 11), Leu-M3 (CD 14), HLA-DR, Transferrin (Trans) ] were measured in monocytes cultured with HAP. After HAP treatment for 24 hrs, the viability of the monocytes was about 95 to 97% in the 0 to 200μg/ml HAP groups. In the 1000μg/ml HAP group, it decreased to about 83%. The monocyte phagocytosis rate increased according to the dose of HAP 1 hr after the treatment of HAP. At 24 hrs after HAP treatment the phagocytosis rate increased slightly slightly in monocytes treated with 0.1μg/ml HAP although it did not change for the group treated with 100μg/ml or less HAP. The protein synthesis of monocytes increased in the 0.1 to 10μg/ml HAP groups compared to the control group, and maximum enhancement (156% of control) was found in the 0.1μg/ml HAP group. DNA synthesis was not affected by the HAP treatment. LDH activity of the monocytes was almost the same for both the control and HAP treated cells 1 hr after the addition of HAP. 24 hrs after the addition of HAP. The LDH activity of monocytes treated with HAP was 3 times higher than the control. AcP activity was not affted by HAP treatment. The occurrance of surface antigens to Leu-15, Leu-M3, HLA-DR and Trans on monocytes showed a tendency to increase due to HAP exposure. These results revealed that the cytotoxicity of HAP was very low for monocytes and that HAP was phagocytized by monocytes soon after attaching to the cells. It is concluded that protein synthesis, LDH activity and surface antigens of the monocytes were stimulated in conjunction with the phagocytosis of HAP.
