The present study has been performed, to test for the influence of epinephrine on the potential difference across the cell membrane (PD) of Madin-Darby canine kidney (MDCK) cells. Under control conditions, mimicking the in vivo situation, PD averages - 53.3 +/- 0.9 mV (n = 37). Increasing extracellular potassium concentration from 5.4 to 10 and 20 mmol/l depolarizes the cell membrane by +4.3 +/- 0.4 mV (n = 5) and +15.8 +/- 1.2 mV (n = 5), respectively. The application of 1 mumol/l epinephrine leads to sustained hyperpolarization of the cell membrane to -71.5 +/- 0.7 mV (n = 37). In the presence of epinephrine, increasing extracellular potassium concentration from 5.4 to 20 mmol/l depolarizes the cell membrane by +30.6 +/- 0.2 mV (n = 5); 1 mmol/l barium depolarizes the cell membrane by +14.8 +/- 0.7 mV (n = 20) and abolishes the effect of step increases of extracellular potassium concentration from 5.4 to 10 mmol/l. In the presence of barium, epinephrine leads to a transient hyperpolarization by -31.2 +/- 1.2 mV (n = 18). During this transient hyperpolarization, the cell membrane is sensitive to extracellular potassium concentration despite the continued presence of barium; 10 mumol/l verapamil depolarizes the cell membrane to -41.0 +/- 2.6 mV (n = 11). In the presence of verapamil, the hyperpolarizing effect of epinephrine is only transient; 10 mumol/l phentolamine depolarizes the cell membrane by +3.0 +/- 0.6 mV (n = 8). In the presence of phentolamine, the effect of epinephrine is virtually abolished (+0.4 +/- 0.6 mV, n = 8); 1 mumol/l isoproterenol depolarizes the cell membrane by +2.8 +/- 0.8 mV (n = 8).(ABSTRACT TRUNCATED AT 250 WORDS)