Reproductive phase dependent daily variation in melatonin receptors (Mel1a and Mel1b), androgen receptor (AR) and lung associated immunity of Perdicula asiatica

Our knowledge about the involvement of melatonin in the regulation of lung associated immune system (LAIS) is still poor though the melatonin receptor types (Mel1a and Mel1b) have been localized in lungs of some wild birds. We thought to explore the correlation between daily variation (within a 24 h time scale) in peripheral melatonin and testosterone along with expression of melatonin receptors (Mel1a and Mel1b) and androgen receptor (AR) in lungs during reproductively active and inactive phases. Receptor expression of Mel1b was more prominent than Mel1a at all the time points during both the reproductive phases. The expression of AR was inversely related to both the melatonin and its receptor expression at the 24 h time scale during both the reproductive phases. Results also reflected a parallel relationship of melatonin, melatonin receptors and all the immune parameters (total leukocyte count, lymphocyte count, % stimulation ratio) suggesting that peripheral melatonin might be responsible for daily periodicity of LAIS. The presence of androgen receptors in lung led us to propose that gonadal steroid does influence the LAIS. Therefore melatonin along with testosterone might be acting as a temporal synchronizer for daily rhythms in lung associated immunity in Perdicula asiatica during different reproductive phases.