Short-term 17-β-estradiol administration does not affect metabolism in young males

We have previously demonstrated that females oxidize more lipid and less protein and carbohydrate during endurance exercise [21], Several studies in male rats have demonstrated similar metabolic changes after 4 d of 17-beta -estradiol (E-2) administration. Our purpose was to study the effects of E-2 administration upon substrate metabolism during 90 min of cycle ergometry at 60% VO(2)peale in 11 healthy, young males. E-2 was administered in a single-blind, cross-over, randomized fashion for 11d (100 mug .d(-1) x 3.5 d --> 200 mug .d(-1) x 3.5 d --> 300 mug .d(-1) x 4.0 d)(.) Respiratory exchange ratio (RER), VO2, Ve, HR, lactate, and glucose were measured every 30 min during exercise and E-2, testosterone TEST, glycerol and triglycerides were measured prior to exercise T = 0 min. Muscle biopsies were taken from the vastus lateralis before and after exercise for glycogen determination. Estradiol treatment resulted in lower plasma TEST (20.8 -->7.8 nmol .L-1, P<0.0001) and higher plasma E-2 (168.1<right arrow>327.3 pmol L-1, P < 0.002). There were no effects of E-2 treatment upon any of the other measured variables including muscle glycogen: (E-2 - PRE = 529.3 --> POST = 237.9; PL-PRE = 582.2 --> POST = 262.4 mmol . kg(-1) [dm]). We concluded that short-term E-2 treatment increased plasma E-2 to female follicular levels in males but had no effect upon lipid or carbohydrate metabolism.