Effect of epidermal growth factor on the membrane potential of cultured porcine thyroid cells

Cultured porcine thyroid cells maintained in media containing TSH exhibited a membrane potential of -50 mV, and hyperpolarized by about 10 mV within 1 h of the addition of epidermal growth factor (EGF; 10 ng/ml). Follicle cells had depolarized to -45 mV after 4 h of exposure to EGF. Cells maintained in dibutyryl cyclic AMP (dbcAMP) did not alter their membrane potential when exposed to EGF for up to 4 h. Cultures washed to remove the TSH or dbcAMP hyperpolarized to -75 mV within 30 min, and a reversible depolarization to -60 mV was observed on addition of EGF. It was concluded that EGF acts as a physiological antagonist of TSH and also exerts a separate depolarizing influence on cultured thyroid cells.