Muscle fiber type characteristics in females with chronic obstructive pulmonary disease. A preliminary study

Abstract

Chronic obstructive pulmonary disease (COPD) is known to elicit intrinsic abnormalities in male skeletal muscle. However, it is unclear to what extent these changes occur in women and whether they are fiber-type specific. We investigated fiber-type specific differences in selected histochemical properties in muscle obtained from women with moderate to severe COPD compared to healthy control (CON) women. Tissue was obtained from the vastus lateralis in five COPD patients (age 66.9 +/- 2.6 years; FEV1 = 43 +/- 7%) and eight CON (age 68 +/- 4.9 years; FEV1 = 113 +/- 4.2%). Compared to CON, the distribution (30.6 +/- 5.2 vs. 57.9 +/- 4.6%) and cross sectional area of type I (CSA, 5660 +/- 329 vs. 3586 +/- 257 microm2) and type IIA (2770 +/- 302 vs. 2099 +/- 206 microm2) were lower (P < 0.05) and higher (P < 0.05), respectively, in COPD. Disease state did not alter either the distribution or CSA of the IIA, IIAX or type X subtypes. Although differences were found between fiber types in the number of capillary contacts (n) (I > IIAX, IIX; IIA > IIX) and the capillaries per CSA (microm210(-3)) (I < IIA, IIAX, IIX), no differences were found between CON and COPD. Succinic dehydrogenase activity and sarcoplasmic reticulum (SR) Ca2+-ATPase activity, measured photometrically (OD units), were higher (P < 0.05), and lower (P < 0.05), respectively, in type I compared to the type II fiber subtypes. These properties were not altered with COPD. COPD in females is accompanied by a higher percent of type II fibers, a larger CSA of type I and type IIA fibers, both of which occur in the absence of differences in oxidative potential and the potential for SR Ca2+-sequestration.