Stimulation of formation of inositol phosphates in primary cultures of bovine adrenal chromaffin cells by angiotensin II, histamine, bradykinin, and carbachol.

Abstract

Histamine, bradykinin, and angiotensin II stimulate release of catecholamines from adrenal medulla. Here we show, using bovine adrenal chromaffin cells in culture, that these agonists as well as carbachol (with hexamethonium) stimulate production of inositol phosphates. The histamine response was mepyramine sensitive, implicating an H1 receptor, whereas bradykinin had a lower EC50 than Met-Lys-bradykinin, and [Des-Arg9]-bradykinin was relatively inactive, implicating a BK-2 receptor. Total inositol phosphates formed in the presence of lithium were measured, with histamine giving the largest response. The relative contribution of chromaffin cells and nonchromaffin cells in the responses was assessed. In each case chromaffin cells were found to be responding to the agonists; in the case of histamine the response was solely on chromaffin cells. When the inositol phosphates accumulating over 2 or 5 min, with no lithium present, were separated on Dowex anion-exchange columns, bradykinin gave the greatest stimulation in the inositol trisphosphate fraction, whereas histamine gave a larger inositol monophosphate accumulation. On resolution of the isomers of stimulated inositol trisphosphate after 2 min of stimulation, the principal isomer present was inositol 1,3,4-trisphosphate in each case. Two hypotheses for the differential responses to histamine and bradykinin are discussed.