Nandrolone decanoate does not enhance training effects but increases IGF-ImRNA in rat diaphragm

To examine whether concomitant anabolic steroid treatment combined with tra ining might enhance previously observed training effects (A. Bisschop, G. G ayan-Ramirez, H. Rollier, R. Gosselink, R. Dom, V. de Beck, and M. Decramer . Am. J. Respir. Grit. Care Med. 155. 1583-1589, 1997) and whether insulin- like growth factor I(IGF-I) was involved in these changes, male and female rats were submitted to inspiratory muscle training (IMT) for 8 wk (30 min/d ay, 5 times/wk) and were compared with untrained controls. During the last 5 wk of training, trained rats were divided to receive weekly either low-do se (LD; 1.5 mg/kg) or high-dose (HD; 7.5 mg/kg) nandrolone decanoate or sal ine for the IMT and control rats. In both sexes, diaphragm muscle mass and contractile properties were unchanged with treatment. In males, HD resulted in decreased diaphragm type I cross-sectional area (-15%; P < 0.05, HD vs. IMT), whereas no changes were observed in females. Finally, an increase in IGF-I mRNA levels was present in HD male(+73%; P < 0.05, HD vs. IMT) and f emale treated rats [LD(+58%) and HD (+96%) vs. IMT; P < 0.001]. We conclude that administration of nandrolone decanoate did not enhance the previously observed training effects in rat diaphragm, although it increased the IGF- I mRNA expression levels.