ACTIVITY OF DEHYDROGENASES AND ENZYMES OF NITROGEN-METABOLISM CARDIACTISSUE AND SKELETAL-MUSCLE OF STEERS FED MONENSIN

Activites of lactate dehydrogenase (E.C.1.1.1.27), malate dehydrogenas e (E.C.1.1.1.40), 2-oxoglutarate dehydrogenase, (E.C.1.2.4.2) glutamat e dehydrogenase (E.C.1.4.1.3), glutamin synthetase (E.C.6.3.1.2), argi nase (E.C.3.5.3.1), ornithine carbamoyltransferase (E.C.2.1.3.3), aspa rtate aminotransferase (E.C.2.6.1.1) and alanine aminotransferase (E.C .2.6.1.2) were measured in cardic and skeletal muscles of steers fed r ation with or without monensin. Steers, 9 months old at the beginning, were fed concentrate, molasses, grass, lucerne and maize chaff. Five steers received monensin in amount of 0.5 mg per 1 kg of live body mas s per day. Control ration, without monensin was fed to the other five steers. After 10 months steers were slaughtered and activity of enzyme s assayed in the mitochondrial and cytoplasmic fraction of cells. Mone nsin increased activity of 2-oxoglutarate dehydrogenase and decreased activity of glutamate dehydrogenase in both fractions of the skeletal muscle tissue. Enzymatic activities found in heart mitochondria were h igher in monensin-fed steers than in control steers. Steers given mone nsin gained 8.23 % more than control steers (263 vs 243 kg).