EFFECTS OF ORCHIECTOMY ON EDL MUSCLE ULTRASTRUCTURE AND ENERGY-SUPPLYING ENZYMES IN GROWING MALE GUINEA-PIGS

To investigate the influence of androgens on muscle maturation during growth, guinea pigs were orchiectomized (CX) or sham operated (SO) at the end of weaning. Extensor digitorum longus (EDL) muscles were removed at weeks 4, 8, and 12 of postnatal development. According to their contractile and metabolic characteristics, four fiber types were distinguished, called I, IIa, IIb(ox), and IIb(glyc). Muscle maturation consisted of a concomitant decrease in percentages of type IIa and IIb(glyc) fibers and increase in the percentage of IIb(ox) fibers in both groups. At week 12, fiber distributions were not different between the two groups. Citrate synthase activity fell and phosphofructokinase and lactate dehydrogenase (LDH) activities rose from week 4 to week 12 and were the same in CX and SO. Muscular LDH subunits increased in SO and decreased in CX during this period. In conclusion, fiber type distribution and enzyme activities at puberty were not androgen dependent in guinea pig EDL muscle. Conversely, these hormones acted on LDH isozyme distribution through the enhancement of the most glycolytic LDH fractions.