Changes in extrathyroidal conversion of thyroxine (T4) to 3,3',5-triiodothyronine (T3) in vitro during development and aging of the rat.
Changes with age in the rate of in vitro conversion of thyroxine (T4) to triiodothyronine (T3) by organ homogenates were determined in female Wistar rats from 6 days to 18 months old. The conversion rates in liver and kidney homogenates of pups before day 13 are very low, and then rise to reach the maximum value at around day 23. During the period of sexual maturation the conversion activity suddenly decreases, and shows afterwards a gradual decline with age. The activity in both liver and kidney of male rats is higher than that of females except in the immature liver. A sudden rise was observed in the conversion activity of organ homogenates when the rats were released from a period of restricted food intake which started at an early age before maturity was achieved.
D000375:Aging; D000818:Animals; D005260:Female; D005508:Food Deprivation; D007668:Kidney / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D012741:Sexual Maturation; D013974:Thyroxine / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
D014284:Triiodothyronine; D013974:Thyroxine