Calcium Induced Modulation of Peripheral-Type Benzodiazepine Receptors in Rat Kidney Membranes

Abstract

The effects of Ca²⁺ ions on ³H-RO 5–4864 binding to the peripheral benzodiazepine receptor were examined. Preincubation of rat kidney membranes with Ca²⁺ at 37°C produced a dose-dependent inhibition of ³H-RO 5–4864 binding. No inhibition was observed in membranes preincubated at 0°C.

The effect of Ca²⁺ was competitive in nature and was fully reversed by the addition of EGTA. At 1 mM, the maximal effect was achieved with CaCl₂, whereas CoCl₂ and CdCl₂ had lesser effects. No other divalent cation salts examined decreased ³H-RO 5–4864 binding to rat kidney membranes. Collectively, these data demonstrate that the affinity of ³H-RO 5–4864 binding to rat kidney membranes is regulated by Ca²⁺ and suggest the presence of cation recognition binding sites coupled to the peripheral benzodiazepine receptor.