INHIBITOR OF PROTEIN-SYNTHESIS PHASE-SHIFTS THE CIRCADIAN OSCILLATOR AND INHIBITS THE LIGHT INDUCED-PHASE SHIFT OF THE MELATONIN RHYTHM IN PIGEON PINEAL CELLS

Our recent study showed that dissociated pigeon pineal cells expressed a circadian oscillation of melatonin release which entrained to light-dark cycle and persisted under constant darkness in vitro, suggesting that pigeon pineal cells contain the circadian oscillator and photoreceptors. Six-hour pulses of anisomycin, an inhibitor of protein synthesis that acts at the 80S ribosomal subunit, induced steady state and phase-dependent phase shifts of the circadian oscillation of melatonin release. The phase advances and delays were produced at CT 7.9 h and between CT 18.6 h and CT 4.5 h, respectively. The magnitudes of phase shifts were dose dependent and correlated with the magnitudes of inhibition of protein synthesis determined at CT 4.5 h. Furthermore, anisomycin blocked the light-induced phase advance. Two dimensional electrophoresis revealed that synthesis of two proteins with Mr of 17,600 and less than 5000 are stimulated by a 3-h light pulse at CT 18.6 h which corresponds to the light-induced phase advance region. These results suggest that 80S ribosomal protein synthesis is involved in normal or light-entrainment functions of the circadian oscillator in pigeon pineal cells.