K + release from rat parotid cells: An α 1-adrenergic mediated event

Abstract

To characterize α-adrenergic receptors in rat parotid gland tissue, 9,10-[9,10- 3H(N)]-dihydro-α-ergocryptine ([ 3h]dhe) and [ 3H]prazosin binding to membranes and stimulated K + release from parotid cell aggregates were examined. Prazosin (selective α 1-adrenergic antagonist), displacement of [ 3H]DHE binding from parotid membranes was biphasic, indicating the presence of both α 1- and α 2-adrenergic receptors. The numbers of α 1- and α 2-receptors were about equal. α 1-Adrenergic receptors were further studied by [ 3H]prazosin binding. [ 3H]Prazosin binding was a rapid, reversible, saturable and stereospecific process, with high affinity ( K D = 0.38 nM) and low capacity ( B max = 380 fmoles ligand bound/g tissue, 10.1 fmoles/mg protein) as determined by Scatchard analysis. The characteristics of [ 3H]prazosin binding were in good agreement with those of catecholamine-stimulated K + release, suggesting that K + release from rat parotid gland cells is an α 1-adrenergic mediated effect.