The amount of NO released following addition of NO donor S-nitrosoglutathione (GSNO) to our experimental buffer (KRH; see below) was measured using an Apollo 1000 Free Radical analyser with an ISO-NOPF100 NO microsensor (1 mm) (World Precision Instruments, USA). The sensor was calibrated with S-nitroso-N-Acetyl-D,L-Penicillamine (Toronto Research) in 0.1 M CuCl2 solution 22 (link). Data were acquired using a Powerlab 2/25 and recorded in LabChart 8.1 (ADInstruments, New Zealand).