Abstract
In the present study we have investigated the influence of bradykinin on the potential difference across the cell membrane (PD) of Madin Darby Canine Kidney (MDCK)-cells. In the absence of bradykinin PD averages -52.6 +/- 0.9 mV (n = 52). Increasing extracellular potassium concentration from 5.4 to 10 and 20 mmol/l depolarizes the cell membrane by +5.2 +/- 0.3 mV (n = 8) and +14.9 +/- 1.0 mV (n = 9), respectively. The application of 0.1 mumol/l bradykinin leads to a transient hyperpolarization of the cell membrane to -70.3 +/- 0.6 mV (n = 30). During this transient hyperpolarization increasing extracellular potassium concentration from 5.4 to 10 and 20 mmol/l depolarizes the cell membrane by +10.4 +/- 0.7 mV (n = 10) and +29.2 +/- 0.8 mV (n = 8) respectively. Application of fragments of bradykinin (0.1 mumol/l) are without significant effect on the potential difference across the cell membrane. 1 mmol/l barium depolarizes the cell membrane by +15.8 +/- 1.2 mV (n = 9) and abolishes the effect of step increase of extracellular potassium concentration from 5.4 to 10 mmol/l. In the presence of barium, bradykinin leads to a transient hyperpolarization by -24.7 +/- 1.3 mV (n = 7). During this transient hyperpolarization, the cell membrane is sensitive to extracellular potassium concentration despite the continued presence of barium. In the nominal absence of extracellular calcium, bradykinin leads to a transient hyperpolarization, which can be elicited only once. The transient hyperpolarization is not affected by the presence of verapamil or indomethacin. In conclusion, bradykinin hyperpolarizes MDCK-cells by increasing the apparent potassium conductance.(ABSTRACT TRUNCATED AT 250 WORDS)
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