Lactate dehydrogenase activity and lactate/pyruvate ratio in muscle of thermally acclimated goldfish.

1. Some glycolytic metabolites were determined for red muscle (RM) and white muscle (WM) of goldfish acclimated to 10 and 25 degrees C. 2. Lactate/pyruvate (L/P) was higher in RM than in WM. 3. Lactate dehydrogenase (LDH) of RM was slightly more susceptible to inhibition by lactate than WM-LDH. At L/P found in vivo under resting conditions, RM-LDH was about three times as inhibited as WM-LDH. 4. When 25 degrees C-fish were forced to swim at 25 degrees C, the increase of L/P in WM was mainly due to increased lactate level and that in RM was ascribed to decreased pyruvate level. These changes were obscure in 10 degrees C-fish.