Removal of ovarian hormones affects the ageing process of acetate metabolism

BACKGROUND: Despite a close association between gastrointestinal motility and sex hormones, it has been unknown whether ovarian hormones affect absorption and metabolism of nutrients. The aim of this study is, therefore, to evaluate metabolism of acetate in rats with age and the influence of ovariectomy on its change. METHODS: Fourteen female rats of the F344 strain were used, and 13C-acetate breath test was performed at 2, 7 and 13 months of age. Seven rats were ovariectomized at three weeks of age (ovariectomy group) and the remaining seven rats were studied as control group. After 24-hr fasting, rats are orally administrated 1ml of water containing sodium (13)C-acetate (100mg/kg) and housed in an animal chamber. The expired air in the chamber is collected in a breath-sampling bag using a aspiration pump. The (13)CO(2) concentration is measured using an infrared spectrometer for 120 min and expressed as delta per mil. RESULTS: The breath (13)CO(2) excretion increased with time and peaked 30 min in control rats. In ovariectomized rats, thee peak time of (13)CO(2) excretion was prolonged to 40 min at 7 and 13 months of age. Cmax was significantly higher at 2 months of age but lower at 4 months of age in ovariectomized rats than in control rats. Those of two groups became equal at 7 months of age. CONCLUSIONS: From the viewpoint of acetate metabolism, removal of ovarian hormones might make rats to be precocious ones and accelerate ageing.