Aluminum salts induce the accumulation of neurofilaments in perikarya of NB2a/dl neuroblastoma

Abstract

NB2a/dl neuroblastoma cells were exposed to aluminum chloride or aluminum lactate (0.1–1 mM) for 3 and 6 days. Additional cultures were exposed to aluminum salts as the cells were stimulated to elaborate axonal neurities by dibutyryl cyclic AMP. By phase-contrast microscopy, aluminum salts had no effect on the morphology of undifferentiated (NB2a(−)) or differentiated (NB2a(+)) cells, or on neuritic elaboration and maintenance. Silver staining by the Bielschowsky method, however, demonstrated argyrophilic accumulations in perikarya of many NB2a(−) and NB2a(+) cells treated with aluminum salts. At the ultrastructural level, whorls of intermediate filaments were the most prominent abnormalities in neuronal perikarya. Although phosphorylated high-molecular weight neurofilament subunits (NF-H) are normally detected by immunocytochemical analyses only within axonal neurites of NB2a/dl cells, aluminum salt treatment caused the detection of phosphorylated epitopes of NF-H within perikaryal of NB2a(−) and NB2a(+) cytoskeletons, suggesting that the argyrophilic filamentous accumulations are composed at least partly of phosphorylated NF-H.