Characterization of bradykinin-stimulated release of noradrenaline from cultured bovine adrenal chromaffin cells

Bovine adrenal chromaffin cells were purified and maintained in culture. On exposure to bradykinin they released noradrenaline. The characteristics of this stimulus secretion were compared with the response to elevated extracellular potassium. Bradykinin released noradrenaline with an EC50 of about 2 nM, with maximum release (2-3 times control incubations) less than that elicited by high potassium or nicotine. Bradykinin analogs showed the response to have characteristics of a B2 receptor. On continuous exposure to 10 nM bradykinin the rate of release was maximal in the first 1 to 3 min, with a further slower sustained rate of release. The response is mostly, but not completely, dependent on extracellular calcium, and was inhibited by cadmium in the micromolar range. Whereas the potassium-stimulated release was highly sensitive to dihydrophyridines, the bradykinin response was not attenuated by dihydropyridine calcium channel antagonists. The results are discussed with respect to stimulus-secretion mechanisms possibly involved in the bradyininin-stimulated release in the light of previous observations characterizing a phosphoinositide response to bradykinin in these cells.