Effect of cold exposure on thyroid hormone in Fischer 344 rats of increasing age.
Male rats aged 6 weeks, 6 months, and 18 months were kept at 4 to 5 degrees C for 12 days and compared with age-matched controls at room temperature as to survival, weight change, food consumption, core body temperature, and several parameters of thyroid hormone economy. After 12 days in the cold, 14%, 50%, and 71% of 6-week-, 6-month-, and 18-month-old rats, respectively, were living. Weight declined in both older groups, though at a faster rate in the oldest. Increasing age did not affect serum T3, rT3, TSH, or the ability to convert T4 to T3 by 20% liver homogenate. Cold exposure, however, resulted in an increase in serum T3 and a decrease in T4 to T3 conversion by liver homogenate in a similar magnitude both in mature and early senescent rats.
D000222:Adaptation, Physiological; D000375:Aging; D000818:Animals; D001831:Body Temperature; D003080:Cold Temperature; D005247:Feeding Behavior; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D013963:Thyroid Hormones; D014284:Triiodothyronine; D013974:Thyroxine