Aim: 

of present study was to examine the early post-embryonic changes in gene expression and activity of two main enzymes: arylalkylamine-N-acetyltransferase (AA-NAT) and hydroxyindole O-methyltransferase (HIOMT) participating in melatonin synthesis with particular attention to the season of hatch.

Methods: 

Experiments were performed in winter and summer on male Hi-Line chickens kept from the day of hatch in an artificial photoperiod L:D 12:12. On the days 2, 9 and 16 after hatch chickens were killed at ZT 11 and ZT 17 (i.e. at the end of light and in the middle of darkness). Pineal glands were dissected out and immediately frozen in liquid nitrogen. Pineal AA-NAT and HIOMT activity was assayed via the liquid biphasic diffusion method. Profiles of AA-NAT, HIOMT and housekeeping gene (TATA box binding protein - TBP) mRNA were measured using real-time RT-PCR.

Results: 

AA-NAT activity and mRNA levels were elevated in darkness increased with age and were higher in summer than in winter. On the contrary, HIOMT activity and mRNA levels reached maximal values during the light phase were higher than that of AA-NAT and change with age and season.

Conclusions: 

Seasonal differences in the activity and mRNA level of pineal enzymes observed in constant laboratory conditions suggest the existence of a photoperiodic memory in the chicken pineal gland. The molecular mechanism of this phenomenon is currently under investigation.

Supported by Internal BST Grant from Faculty of Biology, University of Warsaw.