Circulating thyronines and peripheral monodeiodination in lactating rats.
The well known metabolic and endocrine adaptive responses accompanying lactation include a change in circulating thyronines that resembles the so-called euthyroid sick syndrome. To analyze the role played by tissue monodeiodination in this state, circulating levels of thyronines as well as hepatic and mammary 5'-monodeiodinative activity (5'MA) were assessed during lactation in rats. Results show that the serum iodothyronine changes that accompany lactation are associated with a significant decrease in hepatic 5'MA and a simultaneous increase in mammary 5'MA. These changes begin within the first postpartum day, are proportional to lactation intensity (litter size), and disappear 48 h after either precocious (1st postpartum day) or natural (21st postpartum day) weaning. These data demonstrate that the compartmentalized change in energy expenditure characteristic of lactation is accompanied by organ-specific and opposite adjustments in hepatic and mammary monodeiodinative pathways.
Valverde
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Departamento de Fisiologia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria.
Aceves
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D000818:Animals; D005260:Female; D007453:Iodide Peroxidase / Q000378:metabolism*; D007455:Iodine / Q000378:metabolism; D007774:Lactation / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008321:Mammary Glands, Animal / Q000201:enzymology; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood*; D014285:Triiodothyronine, Reverse / Q000097:blood*
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D007455:Iodine; D007453:Iodide Peroxidase; D013974:Thyroxine