Santos J S, de-Paula E F, Correa T G, de-Freitas L C, da-Fonseca L M, Gutfilen B, Bernardo-Filho M
Instituto de Física, Universidade do Estado do Rio de Janeiro, Brasil.
Braz J Med Biol Res. 1995 Jan;28(1):131-5.
Since the introduction of technetium-99m (99mTc) and its rapid acceptance as a tool in nuclear medicine, very little information is available about its biological action as 99mTc-radiopharmaceuticals. We have determined if cyclophosphamide, an alkylating agent, used in oncology as a chemotherapeutic drug, modifies the binding of 99mTcO-4 and 99mTc-MDP (99mTc-methylenediphosphonic acid) to blood cells and to plasma proteins. The radiopharmaceuticals were injected intravenously (iv) into SW-55 mice (male and female, weight 25 g) and samples of plasma and blood cells were separated. Cyclophosphamide (50 micrograms) was injected iv 1 h before the radiopharmaceuticals. Samples of plasma and blood cells were also precipitated with 5% trichloroacetic acid and soluble and insoluble fractions were isolated. The following results were obtained: 1) cyclophosphamide did not alter (0.25 to 8 h) percent radioactivity of 99mTcO-4 in plasma or blood cells but increased the binding of 99mTc-MDP to blood cells; 2) cyclophosphamide did not alter (0.25 to 8 h) the binding of 99mTcO-4 in insoluble fraction of plasma and decreased (1 to 4 h) percent radioactivity of 99mTc-MDP in the insoluble fraction of plasma; 3) cyclophosphamide increased (0.25 to 4 h) percent radioactivity of 99mTcO-4 in the insoluble fraction of blood cells but did not alter the binding of 99mTc-MDP. Cyclophosphamide and/or its metabolites modified the effective half-life of these radiopharmaceuticals (to 99mTcO-4 was increased 2.3 to 3.4 h and to 99mTc-MDP was decreased 3.3 to 2.1 h) and possibly increased the permeability of blood cells to 99mTcO-4.
自从锝-99m（99mTc）问世并迅速成为核医学中的一种工具以来，关于其作为99mTc放射性药物的生物学作用的信息非常少。我们已经确定，作为肿瘤化疗药物使用的烷化剂环磷酰胺是否会改变99mTcO-4和99mTc-MDP（99mTc-亚甲基二膦酸）与血细胞和血浆蛋白的结合。将放射性药物静脉注射（iv）到SW-55小鼠（雄性和雌性，体重25 g）体内，然后分离血浆和血细胞样本。在注射放射性药物前1小时静脉注射环磷酰胺（50微克）。血浆和血细胞样本也用5%三氯乙酸沉淀，并分离出可溶和不溶部分。得到以下结果：1）环磷酰胺在0.25至8小时内未改变血浆或血细胞中99mTcO-4的放射性百分比，但增加了99mTc-MDP与血细胞的结合；2）环磷酰胺在0.25至8小时内未改变血浆不溶部分中99mTcO-4的结合，并降低了血浆不溶部分中99mTc-MDP在1至4小时内的放射性百分比；3）环磷酰胺增加了血细胞不溶部分中99mTcO-4在0.25至4小时内的放射性百分比，但未改变99mTc-MDP的结合。环磷酰胺和/或其代谢产物改变了这些放射性药物的有效半衰期（99mTcO-4的有效半衰期增加了2.3至3.4小时，99mTc-MDP的有效半衰期降低了3.3至2.1小时），并可能增加了血细胞对99mTcO-4的通透性。
