Effect of epidermal growth factor (EGF) on Tetrahymena pyriformis

Tetrahymena has receptors for hormones characteristic in higher animals and signal transduction systems for provoking response. In the present experim ents EGF, a potent mitogen of epithelial cells were studied. In a 24 h expe riment 1 h treatment with different concentrations of EGF (0.1-10 mug) sign ificantly decreased the growth of Tetrahymena. Five microgram EGF treatment 24 h after 5 mug EGF pretreatment (imprinting) also significantly reduced the amount of cells, and this was moderately, however significantly less, t han without the repeated treatment. After 48 h there was not difference bet ween the amount of single or double treated cells. EGF was chemorepellent i n chemotaxis experiments and 4 h EGF pretreatment abolished this effect, po ssibly by down regulation. The experiments call attention to the effect of EGF at a very low phylogenetic level, however the direction of the effect w as the opposite of the effect in higher animals.