Endothelin‐induced intracellular Ca2+ mobilization through its specific receptors in murine peritoneal macrophages

Abstract

We studied the presence of specific binding sites for endothelin (ET) and the effect of ET on cytosolic free Ca²⁺ concentration ([Ca²⁺]_i) in murine thiogylcolate‐activated peritoneal macrophages. Scatchard analysis for binding experiments using [¹²⁵I]ET‐1 or [¹²⁵I]ET‐3 revealed the existence of a single class of binding sites. The binding parameters (K??? and B???) for [¹²⁵I]ET‐1 were almost identical to those for [¹²⁵I]ET‐3. In addition, unlabeled 3 ET isopeptides (ET‐1, ET‐2 and ET‐3) inhibited the specific binding of both ET‐1 and ET‐3 with similar inhibitory potencies. All 3 ET isopeptides caused an increase in [Ca²⁺]_i in the same dose‐dependent manner (0.01–100nM). These results demonstrate the existence of an ET receptor with the same affinity for all isoforms that mediates the ET‐induced intracellular Ca²⁺ mobilization in murine peritoneal macrophages.