[Patterns of adaptive mobilization of proteins from skeletal muscles during development of compensatory hypertrophy of internal organs].

These studies were dealing with muscle protein depletion in rats under the heart hypertrophy induced by aorta coarctation or under liver regeneration after partial hepatectomy. The last experimental model was also used in order to establish how far such protein mobilization from muscles is realized during their simultaneous adaptation to local overload or disuse induced by a surgical method. 3 and 7 days after induction of hypertrophy of organs investigated, the quantities of sarcoplasmic, myofibrillar and stroma proteins were measured in last-twitch (m. extensor digitorum longus, m. biceps brachii) and slow-twitch (m. soleus) muscles. The contributions of protein biosynthesis and/or protein degradation change into muscle protein loss were evaluated by specially elaborated radiotracer method. The data obtained demonstrate that the pattern of muscle protein mobilization depends on nature of organ and rate of its hypertrophy. The process occurs differently in muscle of different type and in various muscle structures. It appears to be potentiated in overloaded muscles and to a lesser extent in unused ones. The loss of muscle proteins is certainly associated with inhibition of their biosynthesis. Increased degradation (or release) of preformed (non-labelled) protein molecules may also contribute to this loss whereas degradation of newly-formed (labelled) molecules does not change appreciably, possibly because their distribution in muscle structures is non-uniform.