The effects of sex steroids and related menstrual cycle hormones on muscle metabolism

Abstract

Utilizing a pig model, it was the purpose of this in vitro investigation to examine the effects of female sex steroids, either alone or in combination with epinephrine or β-endorphin (endorphin), on the muscle metabolism parameters of glycogen synthesis, C02 production, lactate accumulation, and lip id synthesis. Porcine muscle samples were obtained, separated into strips, and incubated in triplicate in a stock solution containing Krebs-Henseleit buffer, glucose, palmitate, and labeled glucose or palmitate. In Experiment 1, flasks received either high or low dosages of progesterone, estradiol-17β (estradiol), or endorphin. The recovery of label from glucose in glycogen, CO2, and lactate and the incorporation of palmitate into neutral lipids were determined by standard laboratory procedures. In Experiment 2, one-half of the flasks contained estradiol at the beginning of the incubation. After preincubation for 30 min, the flasks received epinephrine at final concentrations varying from 0.01 μM to 10 μM, and the recovery of label from glucose in glycogen was determined. In Experiments 3 and 4, some of the flasks contained progesterone, estradiol, or no hormone at the beginning of incubation. After 30 min preincubation, one-half of the flasks received epinephrine at a final concentration of 10 μM or endorphin at a final concentration of 1 ng/ml. The recovery of label from glucose in glycogen, CO2, and lactate was determined. Samples treated with estradiol displayed a significant increase in glycogen synthesis and lactate accumulation relative to control samples. Muscle preincubated with either estradiol or progesterone and receiving epinephrine after 30 min exhibited significant decreases in glucose recovery in glycogen and lactate, β-endorphin had no effect on glycogen synthesis, lactate, or CO2 production. Based on the findings of the present study, the following conclusions were established: 1. Estradiol enhances the utilization of glucose by the tissue resulting in increases in both glycogen synthesis and lactate accumulation. 2. Epinephrine exerts a glycogenolytic effect in porcine muscle 3. Estradiol and progesterone potentiate the effect of epinephrine on glycogen synthesis. 4. β-endorphin had no effect on the accumulation of glucose carbon in glycogen, lactate, or CO2.