Chiba M, Kikuchi M
Toxicol Appl Pharmacol. 1984 May;73(3):388-94. doi: 10.1016/0041-008x(84)90090-5.
The effects of the administration of lead and tin on delta-aminolevulinic acid dehydratase (5-aminolevulinate hydro-lyase, ALAD, EC 4.2.1.24) activity in human, rabbit, and mouse blood were studied in vivo. In addition the ability of zinc, manganese, and dithiothreitol (DTT) to restore ALAD activity in the blood of lead- or tin-treated subjects was examined in vitro. Manganese, zinc, and DTT restored ALAD activity in vitro. The optimal concentration of zinc required in vitro was 10(-4) M in blood of lead-exposed humans and lead- or tin-administered mice, and 10(-3) M in blood of rabbits treated with either lead or tin. Even at the optimal concentration of zinc, the reactivating effect was incomplete, the highest recovery being about one-third of the control activity. However, the simultaneous addition of zinc and DTT increased ALAD activity to levels comparable with those of controls. Manganese was less effective than zinc in restoring ALAD activity in vitro; the effective dose was 10(-2) M in the blood of lead-exposed subjects, while little effect was noted in tin-treated subjects. Manganese was as effective as DTT in protecting against the inhibition of ALAD activity in vitro by excessive zinc. In contrast, DTT restored ALAD activity completely in the blood of tin-treated rabbits and produced about an 80% recovery of enzyme activity in the blood of tin-treated mice, but only a 35% recovery in the blood of lead-treated rabbits. These results suggest that the mechanisms by which lead and tin inhibit ALAD activity are different.
在体内研究了铅和锡的给药对人、兔和小鼠血液中δ-氨基乙酰丙酸脱水酶（5-氨基乙酰丙酸水解酶，ALAD，EC 4.2.1.24）活性的影响。此外，在体外检测了锌、锰和二硫苏糖醇（DTT）恢复铅或锡处理受试者血液中ALAD活性的能力。锰、锌和DTT在体外可恢复ALAD活性。体外所需锌的最佳浓度在铅暴露人类血液以及给予铅或锡的小鼠血液中为10^(-4) M，在给予铅或锡的兔血液中为10^(-3) M。即使在锌的最佳浓度下，再激活作用也不完全，最高恢复率约为对照活性的三分之一。然而，同时添加锌和DTT可使ALAD活性增加至与对照相当的水平。在体外恢复ALAD活性方面，锰的效果不如锌；在铅暴露受试者血液中的有效剂量为10^(-2) M，而在锡处理受试者中未观察到明显效果。在体外，锰在防止过量锌对ALAD活性的抑制方面与DTT效果相当。相比之下，DTT可完全恢复锡处理兔血液中的ALAD活性，并使锡处理小鼠血液中的酶活性恢复约80%，但在铅处理兔血液中仅恢复35%。这些结果表明，铅和锡抑制ALAD活性的机制不同。
