FIG 6.

Detection of epinephrine and norepinephrine in serum-SAPI in the absence (A) or presence (B) of V. cholerae. Catecholates were analyzed by HPLC combined with electrochemical detection. (A) Supernatants from serum-SAPI without bacteria after 0 h or 48 h; (B) supernatants from V. cholerae grown in serum-SAPI after 0 h and 48 h of growth. At the start of the experiment (t = 0 h), 0.1 mM norepinephrine (NE) (1.7 × 10⁴ ng ml⁻¹) or 0.1 mM epinephrine (E) (1.8 × 10⁴ ng ml⁻¹) was added. Standards were as follows: 1,000 pg ml⁻¹ norepinephrine, 1,000 pg ml⁻¹ epinephrine, and 1,000 pg ml⁻¹ internal standard (IS) in serum-SAPI. In the chromatograms, norepinephrine and epinephrine eluted at 4.9 min and 6.0 min, respectively. Note the different dilutions of the measured supernatants. Asterisks indicate the peaks assigned to unknown compounds. a.u., arbitrary units.