Problems of [S-methyl-11C]-L-methionine as a protein synthesis marker in the pancreas.

To evaluate the possibility of [S-methyl-11C]-L-methionine as a protein synthesis marker in the pancreas, the effect of various labeling positions in the accumulation and metabolism of 14C-labeled L-methionines (S-methyl-14C, 1-14C and 3,4-14C) was studied. In mouse biodistribution studies, the methionines showed differing patterns of labeling position-dependent pancreatic accumulation. In the case of [S-methyl-14C]-L-methionine, protein-incorporation and methyl-transformation equally served as retention mechanisms in the pancreas, indicating [S-methyl-11C]-L-methionine's unsuitability as a pancreatic protein synthesis marker. For such purposes, [1-11C]-L-methionine is considered more suitable.