NUCLEIC ACID CONTENT OF SKELETAL MUSCLE AND LIVER IN MAMMALS OF DIFFERENT BODY SIZE

1. 1. The concentrationsof RNA and of DNA have been measured in the liver and posterior thigh muscles of a series of adult mammals varying in body weight from the mouse to the horse. 2. 2. RNA concentration per 100 g tissue declines progressively in both tissues with increasing species size. 3. 3. As body weight increases, DNA content decreases in muscle but not in liver, thus indicating that species size affect mean cell size of muscle but not of liver. 4. 4. The total amounts of RNA and of DNA in the liver and in the whole skeletal musculature have been estimated. 5. 5. The total RNA content of liver changes as the 0.77 power of body weight, in agreement with other parameters of protein metabolism, whereas the RNA content of muscle is related to the 0·89 power of body weight over the series of mammals. 6. 6. In both tissues, total DNA content is related to the 0·91 power of body weight. © 1969.