Opioid effects on glucose and eicosanoid metabolism in isolated uterus of ovariectomized and non-ovariectomized restricted diet rats

The effect of a 25-day restricted diet (50% of the normal food intake) on uterine glucose metabolism of ovariectomized (25 days) and non-ovariectomized rats, was studied. Underfeeding reduces (CO2)-C-14 production from (UC)-C-14-glucose in intact animal. However, in spayed rats, results are the opposite. In intact rats receiving a low food intake, the eff ect of the addition to the KRB medium of various agonist opioids, was studied. Dinorphin A did not bring about any change. On the other hand, beta endorphin increased glucose metabolism. Also, the addition of Dago and Dadle increased (CO2)-C-14 production, while their corresponding specific blockers, P-FNA and Naltrindole, reversed it. Ovariectomized rats subjected to food restriction are not affected by opioid agonists. In vitro morphine, like endogenous opioids, increased 14CO2 in intact restricted diet rats. Arachidonic acid metabolism in these rats show that underfeeding brings about a decrease in PGF(2 alpha) and PGE(2), but the addition of morphine does not alter this situation, for which eicosanoids metabolites are not related to the effect of morphine. The morphine eff ect was not altered by naloxone. The subcutaneous injection of morphine increased glucose metabolism in intact underfed animals, while naloxone reduced 14CO2 in spayed rats subjected to underfeeding. It can be concluded that uteri from ovariectomized rats receiving a restricted diet are influenced by a mechanism of upregulation related to endogenous opioids. These likely originate in other tissues, and so prevent us from seeing the morphine effect. (C) 2001 Harcourt Publishers Ltd.