Relationship of cardiac succinic acid oxidase activity to body weight in the rat

¹ Laboratory of Physiological Chemistry, Center for Cardiovascular Research, St. Louis University, and the St. Louis University Surgical Service Laboratories, Veterans Administration Hospital, St. Louis, Missouri

Succinic acid oxidase activity was measured in whole heart homogenates of normal male rats weighing from 0.085 to 0.610 kg and was found to vary when expressed on the basis of wet weight of a sample of heart tissue or on its nitrogen content. Young rats tended to have less succinic acid oxidase activity per milligram of cardiac tissue than did older larger rats. However, the activity of the enzyme system of the homogenized whole heart was found to be directly related to the weight of the animal. This relationship can be expressed by the formula: Y = 19.25 + 52.96 (X – 0.35) where Y is succinic acid oxidase activity of the entire heart in milliliters of O₂ per hour, and X is body weight in kilograms. When cytochrome c was added to the reaction mixture, activity was augmented. However, there was a persistent linear relationship between succinic acid oxidase activity of the homogenized whole heart and body weight.