AMINO-ACID-UPTAKE IN SKELETAL-MUSCLE OF RATS BEARING THE YOSHIDA AH-130 ASCITES HEPATOMA

Rats bearing the Yoshida AH-130 ascites hepatoma show decreased activi ty of neutral amino acid transport in skeletal muscle measured in vivo as the tissue accumulation of the analogue a-amino [1-C-14]isobutyrat e (AIB). The decreased accumulation of AIB observed is not merely a co nsequence of the hypoinsulinaemia present in these animals (as a resul t of tumour burden) since in vitro experiments carried out using incub ations of isolated soleus muscles also showed a decreased uptake of ne utral amino acids. In these preparations the addition of insulin resul ts in similar increases in uptake both in the pair-fed controls and th e tumour-bearing animals, thus suggesting similar insulin sensitivitie s. The decrease in amino acid uptake in soleus muscle is associated wi th a decrease in the activity of system A, while systems L and ASC sho w no particular changes as a result of the tumour growth. The kinetic characterisation of system A in the Yoshida-bearing rats shows a decre ase in V-max together with a decrease in K-M in relation with the pair -fed animals.