ROLE OF SERUM AND ION CHANNEL BLOCK ON GROWTH AND HORMONALLY-INDUCED DIFFERENTIATION OF Spodoptera frugiperda (Sf21) INSECT CELLS.

A neuronal morphological phenotype can be induced in cultured Spodoptera frugiperda insect cells (Sf21) by supplementing serum-containing media with 20-hydroxyecdysone (20-HE) and/or insulin. In this study, the primary objectives were to determine any role of ion channels in mediating the morphological change in cells treated with 20-HE and insulin, and whether serum was required to observe this effect. Results showed serum-free media also induced growth of processes in Sf21 cells, but at a lower percentage than that found previously in cells bathed in serum-containing media. Veratridine, a sodium channel activator, increased cell survival when applied in combination with 20-HE to Sf21 cells, and the effect was blocked by tetrodotoxin (1 μM) a known sodium channel blocker. Cobalt, a calcium channel blocker, showed significant inhibition of cell process growth when applied in combination with both 20-HE and 20-HE plus veratridine. Cobalt also showed significant inhibition of cell process growth when applied in combination with insulin. Thus, some type of sodium channel, as well as a mechanism for transmembrane calcium ion movement, are apparently expressed in Sf21 cells and are involved in the differentiation process. These cell lines may be used in a wide variety of endeavors, including the screening of insecticides, as well as foster basic studies of neurodevelopment and ecdysone action.