A COMPARISON OF THE DIFFERENCES IN THE TOTAL NITROGEN CONTENT OF THE MUSCLES OF THE RAT, RESULTING FROM TREATMENT WITH GROWTH HORMONE AND FROM INANITION
1. The distribution of nitrogen in the bodies of rats treated with purified growth hormone for 23 days, and of rats starved for 6 days, has been studied. 2. Some of the extra nitrogen of the growth hormone-treated animals was found deposited in all the tissues examined, with the exception of the heart and the soleus muscle, but the rate at which the individual muscles grew was not uniform. Pectoralis major, masseter, quadriceps, acromiotrapezius, deep spinal muscle, supraspinatus and the diaphragm grew significantly faster than the body as a whole. 3. All the tissues studied, except the masseter and the soleus muscles, were found to lose nitrogen during inanition. It was observed that, with the exception of the masseter muscle, those tissues gaining protein most rapidly under the influence of growth hormone were those that lost it most rapidly during starvation, and conversely. 4. These results reveal the existence of a group of muscles with protein of greater lability than that of the rest of the body tissues. These muscles respond most vigorously to the deposition of protein during treatment with growth hormone, and suffer most depletion of protein during inanition.