Estradiol Affect Na-dependent Ca 2+ Efflux From Synaptosomal Mitochondria

Abstract. The effects of gonadal steroid hormone, 17β-estradiol (E 2 ), in vitro on rat brain mitochondria Ca 2+ movement were investigated. 2+ mediated by the ruthenium red-sensitive uniporter, while it produced biphasic effect on Na-dependent Ca 2+ efflux. Estradiol at concentrations up to 1 nmol.l −1 decreased the efflux significantly (63% inhibition with respect to the control), and at concentrations above 10 nmol.l −1 increased it exponentially. The maximum inhibiting concentration of estradiol (0.5 nmol.l −1 ) increased the affinity of the uniporter (K m reduced by about 30%), without affecting significantly the capacity (V max ) for Na + . The results presented suggest that estradiol inhibits Na-dependent Ca 2+ efflux from mitochondria and acts on mitochondrial retention of Ca 2+ , which may modulate mitochondrial and consequently synaptosomal content of Ca 2+ , and in this way exerts its role in the homeostasis of calcium in nerve terminals