Changes in certain diurnal hormonal rhythms in developing male rats exposed to adiurnal environmental cues.
It has traditionally been thought that diurnal rhythmicities cannot be entrained to follow adiurnal environmental cues that deviate greatly from a 24-hour periodicity. In this study, exposure of male rats pre- and postnatally to an adiurnal lighting schedule of 9 hours light: 9 hours dark resulted in the entertainment of certain hormonal rhythms (such as plasma corticosterone and plasma TSH) but not of others (such as pituitary TSH and plasma T3). Even though thyroid rhythms were influenced only partially by the shorter, 18-hour day, absolute levels of pituitary TSH and plasma T3 were significantly higher in experimental rats (9 hours light:9 hours dark) than controls (12 hours light:12 hours dark). Whole-body and kidney weights and tail length were also significantly increased in the 9 hours light:9 hours dark animals, suggesting a possible relationship of shorter day cycles to faster growth and higher thyroid hormone levels.
D000818:Animals; D001835:Body Weight; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood*; D003624:Darkness; D008027:Light; D008297:Male; D009929:Organ Size; D051381:Rats; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D013963:Thyroid Hormones; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine; D003345:Corticosterone