Thioredoxin, thioredoxin reductase and glutaredoxin increase with maturation in hooded seals. (A) Thioredoxin reductase (TrxR) activity, (B) glutathione disulphide reductase (GR) activity, (C) thioredoxin (Trx) protein expression and (D) glutaredoxin 1 (Glrx1) protein expression in neonates, weaned pups and adult hooded seals. One unit of TrxR activity is defined as the NADPH-dependent production of 2 μmol 2-nitro-5-thiobenzoate min–1 at 22°C. One unit of GR is defined as the amount of enzyme needed to oxidize 1 nmol of NADPH to NADP+ per minute at 25°C. Data are means ± s.e.m. *, P<0.05.