Effects of melatonin and hypothyroidism on somatomedin levels of female Syrian hamsters.
Female Syrian hamsters maintained on a 14 h light, 10 h dark photoperiod were injected once daily (1-2 h before lights out) with melatonin (25 micrograms), alone or in combination with thiourea, or with thiourea plus thyroxine. Serum levels of the somatomedin, Insulin-like growth factor-I (IGF-I), were significantly reduced by thiourea as well as by melatonin administration. These data suggest that in the female hamster melatonin-induced reduction of circulating IGF-I depends largely on a reduction in circulating levels of thyroid hormones. However, melatonin-induced changes in secretion of thyroid hormones, gonadal hormones, and hypothalamic hormones could contribute to decreased growth hormone (GH)-stimulated somatomedin secretion.
Vriend
J
J
Department of Anatomy, University of Manitoba, Winnipeg, Canada.
Sheppard
M S
MS
Bala
R M
RM
D000818:Animals; D006224:Cricetinae; D003624:Darkness; D004195:Disease Models, Animal; D004338:Drug Combinations; D005260:Female; D013006:Growth Hormone / Q000097:blood; D007037:Hypothyroidism / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000097:blood*; D008027:Light; D008550:Melatonin / Q000494:pharmacology*; D008647:Mesocricetus; D011863:Radioimmunoassay; D013002:Somatomedins / Q000097:blood*; D013890:Thiourea / Q000494:pharmacology; D013974:Thyroxine / Q000494:pharmacology; D014284:Triiodothyronine / Q000097:blood / Q000502:physiology
D004338:Drug Combinations; D013002:Somatomedins; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013890:Thiourea; D008550:Melatonin; D013974:Thyroxine