Figure 4. Production and output of ¹⁵N-labelled agmatine from livers perfused with [guanidino-¹⁵N₂]arginine.

(A) ¹⁵N enrichment (at.% excess) in effluent agmatine. (B) Output (nmol·min⁻¹·g⁻¹) of ¹⁵N-labelled agmatine as determined by the product of ¹⁵N enrichment (at.% excess/100) times total output (nmol·min⁻¹·g⁻¹). Data were obtained from measurements done at the steady-state (i.e. 25–40 min after start of 0.5 mM [guanidino-¹⁵N₂]arginine infusion and other nutrients as indicated under the Materials and methods section without (CON, control) or with the addition of 10⁻⁷ M insulin (+INS), glucagon (+GLU) or 10⁻⁴ M dibutyryl-cAMP. Results are expressed as means±S.D. for three livers. **P<0.05.