摘要：Biological effects of zinc on the lung were examined by biochemical and cytological indicators in the broncho-alveolar lavage fluid. Zinc acetate was instilled intratracheally into male Wistar rats (14 weeks old, mean body weight 371 g) at a dose of 20μg Zn/0.4 ml saline/rat and the animals were killed 1, 3, 6 and 12 h and 1, 2, 3 and 7 d later for the time-dependent experiment. The metal ion was also instilled intratracheally into rats at doses of 0, 5, 10, 20, 50, 100 and 200μg Zn/rat and the animals were killed 2 d later for the dose-dependent experiment. The lung was washed with 5 mM Tris/HCl buffer (pH 7.4, containing 0.25 M glucose, warmed at 37°C) and the broncho-alveolar lavage fluid was centrifuged at 650 g for 5 min, and the supernatant and pellet fractions were used for further examinations. Activities of β-glucuronidase and lactate dehydrogenase and protein content in the lavage fluid were used as biochemical indicators, while numbers of total cells, macrophage and polymorphonuclear leukocytes in the lavage fluid were used as cytological indicators. Concentrations of calcium, magnesium, phosphorus and sulfur were also determined by emission spectrometry. Biological data obtained from time-dependent and dose-dependent experiments indicate that inflammatory responses of the lung can be detected most efficiently two days after intratracheally instillation of zinc acetate. It was suggested that the lung responds to zinc acetate below a dose of 20μg Zn/rat by the native protective mechanism. However, biological indicators were significantly altered at doses more than 20 μg Zn/rat, indicating that the lung was damaged by zinc at a dose of as hight as 20 μg Zn/rat.
