Effect Of Ca++ And Mg++ On The Binding Of Cytoplasmic And Nuclear Estradiol Receptors In Breast Cancer Of Female Patients

Abstract

Specific estradiol receptors were quantitatively determined in the cytosol and nuclear fractions of four cancerous breast tissues and one normal uterus. Validated methods are described for estradiol receptor assay. The number of cytosol receptors was observed to be in the range of 4.1 x 10-3 _ 6.2 x 10"2 pmoles/mg protein, while the number of nuclear receptors was significantly higher compared with cytosol receptors (0.089 to 2.49 pmoles/mg protein). The dissociation constant (K^) of the estradiol receptors, analyzed from the Scatchard plot, was higher in the nuclear pellets than in cytosols of cancerous. The addition of divalent cations (Ca^+ or Mg2+) to the nuclear preparation, altered the binding properties of the receptors in the human uterus; while they altered their physical association state in the cancerous tissues. In the presence of cations, marked activation of the nuclear binding in the cancerous tissues was observed; a pattern which was not clearly observed in the cytosols of the same tissues or in the uterus. However, the receptor's affinity and behaviour of a recurrent tumor, towards the action of these cations were different from that of other investigated tissues.