Opiate-specific displacement of steroid hormones from microsomes.

Opiates displaced [³H]-testosterone in relation to their pharmacological potencies from binding sites on rat liver microsomes. The drugs competed less effectively with progesterone and least with corticosterone. Other drugs tested, including centrally acting ones, were ineffective. These results support our hypothesis that opiate action is mediated through steroid hormone receptors.     

Excretion of corticosteroid metabolites in urine and faeces of rats.

Stress enhances the production of corticosteroids by the adrenal cortex, resulting in the increased excretion of their metabolites in urine and faeces. An intraperitoneal injection of radioactive corticosterone was applied to adult, male Sprague-Dawley rats to monitor the route and delay of excreted metabolites in urine and faeces. Peak concentrations appeared in urine after 3.2 +/- 1.9 h and in faeces after 16.7 +/- 4.3 h. Altogether about 20% of the recovered metabolites were found in urine and about 80% in faeces. Using high-performance liquid chromatography (HPLC), several peaks of radioactive metabolites were found. Some metabolites were detected by enzyme immunoassay (EIA) using two different antibodies (corticosterone, 11beta-OH-aetiocholanolone). There was a marked diurnal variation with low levels of faecal corticosterone metabolites in the evening and higher values in the morning. This diurnal variation was influenced neither by the intraperitoneal injection of isotonic saline nor by ACTH. However, the administration of dexamethasone eliminated the morning peak for 2 days.