Crayfish Procambarus clarkii shows circadian variations in different parameters of the GSH cycle

The present study investigated the rhythmic changes in glutathione status i n midgut gland and hemolymph as well as in glutathione reductase (GR) activ ity in the crayfish Procambarus clarkii. In order to determine the circadia n nature of these rhythms different groups of crayfish were submitted to co nstant-darkness conditions for 24 or 72 It after they had spent 15 days und er light-dark 12:12 cycles. The animals of the different batches were kille d at 6 h intervals during a 24 h cycle. Reduced glutathione (GSH) and oxidi zed glutathione (GSSG) in hemolymph and midgut as well as midgut GR activit y were determined in midgut gland and hemolymph by fluorometric and spectro photometric methods. Data analysis by chronogram and single Cosinor reveale d circadian rhythmicity for GSH and GSSG concentration in both tissues as w ell as midgut GR activity. The rhythm parameters revealed oxidative stress induced by light. The possible correlation between the glutathione rhythm a nd other metabolic and behavioral rhythms of crayfish as well as the import ance of the glutathione circadian temporal order in the adaptation of crayf ish are discussed.