LACK OF EFFECT OF RECOMBINANT HUMAN GROWTH-HORMONE (GH) ON MUSCLE MORPHOLOGY AND GH-INSULIN-LIKE GROWTH-FACTOR EXPRESSION IN RESISTANCE-TRAINED ELDERLY MEN

Vastus lateralis muscle samples were obtained by needle biopsy from 18 healthy elderly men (65-82 yr) participating in a double blind, place bo (PL)-controlled trial of recombinant human GH (rhGH) and exercise a nd assessed for muscle morphology and skeletal muscle tissue expressio n of GH and insulin-like growth factors (IGFs). Subjects initially und erwent progressive resistance training for 14 weeks and were then rand omized to receive either rhGH (0.02 mg/kg BW . day, sc) or PL while un dertaking a further 10 weeks of training. Muscle samples were obtained at baseline and at 14 and 24 weeks. The mean (+/- SEM) cross-sectiona l areas of type I and II fibers were similar (type I, 3891 +/- 167 mu m(2); type II, 3985 +/- 200 mu m(2)) at baseline and increased (P < 0. 01) by 16.2 +/- 4.1% and 11.8 +/- 3.8%, respectively, after the initia l 14-week training period. After treatment (weeks 14-24), two-way repe ated measures ANOVA revealed a main effect of time for type I (P < 0.0 1) and type II fibers (P < 0.05), but no group effect or interaction. The increase in cross-sectional area for the PL group was significant (P = 0.01) for type I (11.5 +/- 3.6%) and approached significance (P = 0.06) for type II fibers (11.1 +/- 5.6%). For rhGH, the change in typ e I (6.3 +/- 5.9%) and II (7.1 +/- 5.2%) fiber area was not significan t. No apparent change in tissue GH receptor, IGF-I, IGF-I receptor, IG F-II, or IGF-II receptor messenger ribonucleic acids occurred as a res ult of exercise after the Ii-week pretreatment period or after treatme nt with rhGH or FL. These results indicate that rhGH administration in exercising elderly men does not augment muscle fiber hypertrophy or t issue GH-IGF expression and suggests that deficits in the GH-IGF-I axi s with aging do not inhibit the skeletal muscle tissue response to tra ining.