To investigate aberrant metabolism of
proline (Pro) and its precursors in
tuberous sclerosis (TS), 6, 7 and 5 strains of control, TS (normal skin) and TS (
tumor) fibroblasts, respectively, were cultured in Eagle's MEM containing dialyzed
fetal bovine serum with or without 0.1 mM
ornithine (Orn).
Ornithine aminotransferase (OAT) activity was decreased in TS, especially in TS (
tumor) after mild sonication treatment. The yield of the OAT
protein was inhibited in TS (
tumor) when cultured without Orn. Free
glutamate (Glu) in the medium was significantly increased in TS (
tumor). Free
proline (Pro) in cells was significantly decreased in TS (
tumor) when cultured with Orn, but
protein-bound Pro was not. The relative concentration of free Glu to
glutamine (Gln) in the medium and that of free Glu to Pro in cells cultured with Orn were increased in TS (
tumor). These results suggest that the requirement for Orn, increased turnover of Pro to Glu and increased elimination of Glu into the medium occur in TS (
tumor). Aberrant regulation or turnover of Pro and Glu metabolism may occur in TS, especially in
tumor cells.