The Jou Printed

findin and s repres respectively. Histochemical fibre-typing, using myosin ATPase staining techniques, has typically shown mouse EDL to consist wholly of type IIA and type IIB fibres in roughly equal proportions (Haida et al. 1989; Klueber et al. 1989). In contrast, mouse soleus has been shown to consist of only type I and type IIA fibres in varying proportions from 31 to 41% type I fibres (Dribin and Simpson, 1977; Lewis et al. 1982; Carnwath and Shotton, 1987; Haida et al. 1989). This variation in percentage of fibre types found in soleus is likely to be caused by the use of different ages, sexes and strains of mice. Energetic studies have complemented these findings and shown that mouse EDL has far higher basal rates of glycolysis and glyconeogenesis (Bonen et al. 1984, 1990), but a lower basal rate of glycogenesis (Bonen et al. 1990) than soleus. Measurements of heat production by mouse EDL and soleus during and after short tetani have given further indications of the differences between these muscles (Leijendekker an