The effect of zinc and pH on the behaviour of delta-aminolevulinic acid dehydratase activity in baboons exposed to lead.

Abstract

Four adult male baboons (Papio ursinus) were exposed to a cloud of lead oxide dust to induce changes in the status of .delta.-aminolevulinic acid dehydratase (ALAD). Enzyme activity fell rapidly to a steady state as blood Pb levels rose above normal. Exogenous Zn activated the enzyme, and the antagonistic effect of Zn on in vivo and in vitro Pb inhibition was demonstrated for baboons. In baboons not exposed to Pb dust, ALAD showed an activity optimum at pH 7.1 which shifted to pH 6.8 with in vitro addition of Pb. In baboons exposed to Pb dust, with raised blood Pb, activity optima were observed at pH 6.8 and 6.2, while the optimum at pH 7.1 was absent.