The alpha 1A-adrenoceptor couples to Ca2+ mobilization in mouse peritoneal macrophages

Activation of the alpha 1-adrenoceptor (alpha 1-AR) in mouse peritoneal macrophages induces a Ca(2+)-dependent K+ current via release of Ca2+ from internal stores [Hara et al. (1991) Pflügers Arch 419: 371-379]. In order to characterize the alpha 1-AR subtype in macrophages, we examined potencies of the alpha 1-AR subtype-selective antagonists against epinephrine-induced increases in intracellular Ca2+ concentration ([Ca2+]i). The Ki values for the alpha 1-AR in macrophages of WB4101, 5-methylurapidil and phentolamine were 0.13 nM, 0.15 nM and 7.0 nM, respectively. (+)-Niguldipine (10 nM) completely blocked the response. Treatment with chloroethylclonidine (CEC) did not abolish the response. These pharmacological properties of the alpha 1-AR in macrophages agree quite well with those of the alpha 1A subtype.