DIETHYLSTILBESTROL ALTERS THE MORPHOLOGY AND CALCIUM LEVELS OF GROWTHCONES OF PC12 CELLS IN-VITRO

Diethylstilbestrol (DES) is a synthetic estrogen with carcinogenic pro perties. DES is known to alter cytoskeletal components, including the organization of actin stress fibres in C6 rat glioma cells. In a test of the hypothesis that DES disrupts actin filaments of growth cones in neuron-like cells, DES-induced changes in filopodial lengths were qua ntified in rat pheochromocytoma (PC12) cells in vitro. DES significant ly altered growth cone morphology, with collapse of growth cone filopo dia and neurite retraction invariably occurring at a concentration of 10 mu M. At 5 mu M DES, transient reductions in total filopodial lengt hs occurred. At DES concentrations of 0.1 nM and 1 nM, reductions in t otal filopodial lengths occurred in a fraction of growth cones. Eviden ce exists which shows that growth cone activity and morphology are int imately linked to levels of intracellular, free calcium and that DES i ncreases such levels. Measurements of free intracellular calcium level s by fluorescence microscopy, at times concurrent with the DES-induced reduction in total filopodia lengths, showed that calcium levels were indeed significantly increased by 10 mu M DES. Labelling of filamento us actin (f-actin) with FITC-phalloidin showed that the f-actin distri bution in growth cones exposed to DES could not be differentiated from the distribution found in spontaneously retracting growth cones. Toge ther with evidence which showed chat growth cone motility was not affe cted, the results are taken to indicate that DES, rather than acting d irectly on the cytoskeleton, exerts its effects indirectly, by a calci um-induced destabilization of actin filaments in the growth cone. (C) 1993 Intox Press, Inc.