Early effect of growth factors (EGF + insulin) upon ATP turnover in 3T3 cells. Inhibition by cytochalasin B and D.

We have demonstrated previously a rapid increase in ATP turnover soon after adding epidermal growth factor (EGF) and insulin to quiescent cultures of Swiss 3T3 cells. In the present work, we tried to determine whether this increase could be correlated with the early stimulation by growth factors of cell movements. We showed that cytochalasin B (CB), in complete or glucose-free medium, inhibited this early increase caused by growth factors, in phosphate incorporation in small organic acid-soluble compounds (Po). Cytochalasin D (CD) specifically inhibited the stimulation caused by growth factors of Po labelling and ATP turnover, but lacked all inhibitory effect on unstimulated cells. The inhibitory effect of CD was transient. We hypothesize that addition of EGF and insulin to quiescent 3T3 cell cultures induces a rapid and transient change in cell movements, which could be responsible for about half of the early increase in ATP degradation and turnover.