title: On the mechanism of opioid-oestradiol interactions.
abstract: Characteristics of opioid binding and possible relationships between oestradiol and opioid binding sites were studied in rat oestrogen sensitive tissues(uterus, preoptic area-anterior hypothalamus, median eminence-basal hypothalamus). Naloxone (Nal) and oestradiol (Oe) bindings were assessed by in vitro saturation analyses. In 800 g supernatants of both uterine and hypothalamic tissues homogenates high affinity (Kd: 2-4 X 10(-9) M) and low capacity [3H]Nal binding sites were found. These binding sites were sedimented from 800 g supernatant by further centrifugation at 10(5) g for 1 h. In competition studies [3H]Nal binding was completely prevented by morphine, while met-enkephalin and leu-enkephalin caused only a partial inhibition. [3H]Nal binding was increased by ovariectomy and decreased by Oe treatment (10 micrograms/100 g b.wt) in both tissues. The cytoplasmic [3H]Oe binding in the studied tissues seems to be affected by the naloxone binding system. After in vitro saturation of naloxone binding sites by naloxone the [3H]Oe binding to low affinity sites (type II) in hypothalamus as well as in uterus has been increased by 8- and 2-fold, respectively. These results indicate the presence of specific [3H]Nal binding in rat uterus with similar properties to those found in the hypothalamus. Furthermore an interaction between opioid and oestradiol receptor systems could be also suggested.
mesh_terms: D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007031:Hypothalamus / Q000032:analysis; D066298:In Vitro Techniques; D009270:Naloxone / Q000378:metabolism; D010052:Ovariectomy; D051381:Rats; D011919:Rats, Inbred Strains; D011959:Receptors, Estradiol / Q000032:analysis*; D011960:Receptors, Estrogen / Q000032:analysis*; D011957:Receptors, Opioid / Q000032:analysis* / Q000187:drug effects; D014316:Tritium; D014599:Uterus / Q000032:analysis*
chemical_list: D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D011957:Receptors, Opioid; D014316:Tritium; D009270:Naloxone; D004958:Estradiol