Fig. 4. Activities of enzymes in liver of rainbow smelt subjected to a controlled decrease in temperature: (A) glyceraldehyde-3-phosphate dehydrogenase (GAPDH); (B) glycerol-3-phosphate dehydrogenase (GPDH); (C) alanine aminotransferase (AlaAT). Values are means ± s.e.m., N=6 at each point with the exception of 1.5°C, where N=5, and –1°C, where N=11. Different letters indicate significant differences between values. Transition time and plasma glycerol levels for this experiment are presented in Fig. 1C.