Fig. 2.

Glutamine nitrogens do not integrate into the urea cycle in vitro. a Immunoblots for ARG2 and ARG1 in AsPC1-shScr and AspC1-shARG2 cells. b Proliferation curves of cells in a (n = 6). Data are representative of 4 independent experiments. c Fractional ¹³C-labeling of urea (M1) and ornithine (M5) in AsPC-1 cells with control (shScr) or ARG2 knockdown (shARG2, hairpins A06 and A10) grown in culture in 0.1% serum and 100 ng ml⁻¹ IGF-1, supplemented with 1 mM ¹³C₆-arginine for 48 h (n = 4). d Diagram of the urea cycle, with metabolites in red indicating significant ¹⁵N-labeling. e Fractional labeling of the indicated metabolites in cells described in a, grown in media supplemented with 2 mM ¹⁵N(amine)-glutamine for 1 h or 24 h (n = 4). Data are representative of two independent experiments. In b, data represent the mean ± s.e.m. In c, e, data represent the mean ± s.d. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001, by one-way ANOVA followed by Tukey test