Divalent cations increase [3H]-prostacyclin binding to membranes of neuronal somatic hybrid cells

1 [3H]-prostacyclin binding to membranes of a highly differentiated neuronal somatic hybrid is increased equally in the presence of Ca2+, Ba2+, Mg2+ or Sr2+ ions. 2 Analysis of the binding of [3H]-prostacyclin in the presence of low (1 mM) or high (50 mM) Mg2+ ion concentrations has revealed a cation-dependent increase in ligand receptor affinity (Kd values = 57.4 nM and 21.9 nM). 3 The increase in [3H]-prostacyclin binding due to divalent cations is not accompanied by an alteration in the maximum binding capacity of the membranes.