[en] An interaction between Ca⁺⁺-channel antagonists and the α₂-adrenergic receptor on active electrolyte transport was demonstrated in rabbit ileum. Clonidine, an α₂-agonist, stimulated NaCl absorption apparently by Ca⁺⁺-channel antagonism since it inhibited ⁴⁵Ca⁺⁺ uptake across the basolateral membrane and decreased total ileal calcium content. This stimulation was inhibited by the Ca⁺⁺-channel antagonists dl- and l-verapamil and cadmium but not by nifedipine. The binding of ³H-yohimbine, a specific α₂-adrenergic antagonist, was studied on purified ileal cell membranes using a rapid filtration technique. dl-Verapamil and Cd⁺⁺ inhibited the specific binding of ³H-yohimbine over the same concentration range in which they affected transport. In contrast, nifedipine had no effect on binding, just as it had no effect on clonidine-stimulated NaCl absorption. These data demonstrate that there is an interaction between Ca⁺⁺-channels and α₂-adrenergic receptors in ileal basolateral membranes. Some Ca⁺⁺-channel antagonists alter α₂-adrenergic binding to the receptor and α₂-agonist binding leads to changes in Ca⁺⁺ entry. A close spatial relationship between the Ca⁺⁺-channel and the α₂-receptor could explain the data