MYOGLOBIN CONTENT OF HAMSTER SKELETAL-MUSCLES

Myoglobin (Mb) may facilitate O2 diffusion in muscle tissue, yet model s of O2 transport are often simplified by ignoring the role of Mb. A r ecent analysis of O2 transport in hamster retractor muscle revealed a large discrepancy between the observed O2 diffusion from arterioles an d that predicted by a mathematical model that did not include Mb. To e stablish whether this simplification was justified, we measured Mb con tent ([Mb]) in three hamster muscles that vary markedly in histochemic al fiber type composition. [Mb] was determined spectrophotometrically using freshly excised tissues from hamsters of different ages (5-34 wk ). [Mb] increased rapidly up to 15 wk of age and then rose more slowly . [Mb] in hamster muscles paralleled oxidative capacity. Our measureme nts of rat and dog muscles also show that [Mb] varies greatly among sp ecies and among muscles of a given species. The results indicate that in the hamster the variability in [Mb] with age and muscle should be t aken into account when the potential role of Mb in studies on O2 trans port is interpreted.