Photoperiodic and light spectral conditions which inhibit circulating concentrations of thyroxine in the male hamster.
Adult male Syrian hamsters were exposed daily for 12 weeks to 11 h/day of cool white fluorescent light (350 +/- 50 microW/cm2) followed by an additional 3 h of near ultraviolet (339-317 nm), blue (435-500 nm), green (515-550 nm), yellow (558-636 nm) or red (653-668 nm) light at an irradiance of 0.2 microW/cm2 or to total darkness. Animals exposed to the wavelengths between 558-668 nm (yellow or red half peak bandwidths) or those receiving a total of 13 h of darkness/day had suppressed circulating levels of thyroxine (T4), a depressed free T4 index (FT4I) and a higher T3/T4 ratio compared to animals receiving a total of 14 h of white light (350 +/- 50 microW/cm2). These results suggest that specific wavelengths of light can affect the neuroendocrine-thyroid axis.
D000818:Animals; D006224:Cricetinae; D008027:Light; D008297:Male; D008550:Melatonin / Q000502:physiology; D008647:Mesocricetus; D010870:Pineal Gland / Q000502:physiology; D012243:Rhodopsin / Q000502:physiology; D013974:Thyroxine / Q000097:blood*
D012243:Rhodopsin; D008550:Melatonin; D013974:Thyroxine