Seasonal variation of myoglobin in the northern red-backed vole

Abstract

A marked increase in myoglobin [Mb] concentration was observed in thigh muscle (1.3 [forward arrow] 3.2 mg/g) and masseter (4.7 [forward arrow] 10.1 mg/g) from northern red-backed voles (Clethrionomys rutilus dawsoni) during winter (Jan.-Feb.) as compared with the minimum summer values (July-Sept.). Heart-Mb showed a more modest change (4.3 [forward arrow] 5.7 mg/g). Because the life span in this species is synchronized to the year, with growth ceasing in fall and resuming in spring, the concentration increase during the fall was by synthesis of Mb, but the decrease during the spring represented dilution of Mb by growth.