Seasonal variation of myoglobin in the northern red-backed vole.

MORRISON, PETER, MARIO ROSENMANN, AND JOHN A. SEALANDER. Seasonal variation of myoglobin in the northern redbacked vole. Am. J. Physiol. 2 I I (6) : 1305-1308. 1966.-A marked increase in myoglobin concentration was observed in thigh muscle (I. 3 -+ 3.2 mg/g) and masseter (4.7 -+ 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 --) 5-7 mg/g>. B ecause 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.