Lead Stimulates Golgi Sialyltransferase at Times Coincident with the Embryonic to Adult Conversion of the Neural Cell Adhesion Molecule (N-CAM)

The neural cell adhesion molecule N-CAM is believed to be intimately involved in the structuring of the central nervous system. During post-natal development the molecule exists in 2 forms--a sialic acid-rich form which is preferentially expressed during cell acquisition and fibre outgrowth and a sialic acid-poor form which appears at times coincident with synaptogenesis. The developmental changes between these 2 forms have been demonstrated to be impaired by chronic low-level lead exposure and this is consistent with the reduced synaptic elaboration associated with this action. Here is described the effect of lead on the Golgi-associated sialyltransferase which regulates N-CAM sialylation state. Lead chloride was found to markedly stimulate sialyltransferase with an ED50 of 5 X 10(-7) M in adult Golgi fractions. This was not observed in fractions derived from 12-day old animals. At the concentration of 5 X 10(-5) M lead was found to have a differential effect on the developmental expression of this enzyme. During the early phases of development (days 4-16) sialyltransferase activity was inhibited. However, in coincidence with periods of N-CAM desialylation (days 16-30), it was significantly stimulated. These findings are related to the perturbations of N-CAM function during chronic low-level lead exposure.