The Effects of Ovarian Hormones on Glucose and Fatty Acid Oxidation during Exercise in Female Ovariectomized Rats

Summary

The effects of ovarian hormones on glucose and fatty acid oxidation during exercise were investigated in adult female ovariectomized rats. Rats subdivided into 3 groups received intraperitoneal injections of hormones or sesame oil for 8 days. Estrogen (E) treated rats received 17-β estradiol in daily doses of 2 μg. Estrogen and progesterone treated rats (EP) received 17-β estradiol in daily doses of 2 μg and 2 mg, respectively. Control rats (S) received sesame oil alone. After an overnight fast, rats ran at the speed of 25 m · min^-1 for 60 min. [U-¹⁴C]glucose or [1-¹⁴C]palmitate was injected into rats at 5 min of exercise and before 10 min of exercise, respectively. Expired ¹⁴CO₂ was collected using bottomless chamber on a treadmill belt. No significant differences were found in mean blood glucose, lactate and plasma free fatty acid concentrations after the exercise. Until the end of the exercise 34.7±2.6 (E, n=5), 40.8±2.9 (EP, n=5) and 43.7± 3.5% (S, n=6) (mean±SE) of ¹⁴C which was injected as ¹⁴C-glucose was recovered as ¹⁴CO₂. During 60 min of the exercise 27.5±1.0 (E, n=7), 19.8±2.7 (EP, n=6) and 25.0±1.9% (S, n=6) of ¹⁴C which was injected as ¹⁴C-palmitate was recovered as ¹⁴CO₂. A significant difference was found in this rate between E and EP (P < 0.05). It was concluded that estrogen treatment stimulated fatty acid oxidation compared with the estrogen plus progesterone treatment and tended to inhibit glucose oxidation during prolonged exercise.

Key-Words

Female Ovariectomized Rat - Estrogen - Progesterone - Exercise - Oxidation