Date of Graduation

2003

Document Type

Dissertation/Thesis

Abstract

Purpose. Severe emphysema affects peripheral skeletal muscle with only partial reversal with exercise training. The effects of mild emphysema on adaptation of peripheral skeletal muscle to different loading conditions are unknown. Methods. Male Syrian golden hamsters were instilled with saline (S, n = 6) or porcine elastase (E, n = 12) to induce mild emphysema prior to removal of the right Achilles tendon to induce overload (OV) of plantaris muscle and unloading (UL) of gastrocnemius. The left limb served as control (C). Six animals were sacrificed at 1, 3, and 5 months. Fiber type, citrate synthase activity (CS), and capillary to fiber ratio (C/F) were measured. Data were analyzed with 3-way ANOVA. Results. There was an interaction of disease, loading, and time, in type IIB fiber % in plantaris and type I fiber % in gastrocnemius, p < 0.05. In plantaris EC was lower at 1 & 3 months (15 vs. 13%; 24 vs. 28% respectively) then increased at 5 months while SC decreased (26 vs. 12%). OV limbs had ∼12% type IIB across time with no difference between groups. In gastrocnemius, type I fiber % was greater in EC at 1 & 3 months (31 vs. 10%; 49 vs. 32% respectively). EC decreased at 5 months while SC increased (9% vs. 26%). UL blunted adaptation in the EC group. CS in plantaris was not different, while CS was higher in E at 1 month in gastrocnemius. There was an interaction of disease and time on C/F in plantaris, p < 0.05. E was higher than S at 1 month, but then declined more than S at 3 & 5 months. Conclusions. Mild emphysema causes peripheral skeletal muscle adaptation early in the disease process. These effects appear to be beneficial to aerobic capacity initially, but become detrimental as lung disease worsens. Chronic overload prevents the effects of worsening disease, while normal loading blunts them. Chronic unloading does not exacerbate disease effects.

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