Acute and chronic leptin effect upon in vivo and in vitro rat thyroid iodide uptake.
Leptin has stimulatory effects on the hypothalamic-pituitary-thyroid axis and on deiodinases activities. Here, we evaluated the effect of leptin injection upon in vivo and in vitro thyroid 125I uptake (RAIU). We designed two experiments: acute leptin (LepA) with a single dose of leptin (8 microg/100 g BW/sc), and chronic leptin (LepC), injected with the same dose of LepA, once a day, for 6 days. In parallel, control groups were saline-injected. For in vivo study, part of the animals were injected with 125I (3700 Bq) and killed after 15 or 120 min. In vivo thyroid RAIU was not changed in LepA animals. However, LepC animals showed higher in vivo thyroid RAIU (15 min:+130% and 120 min:+72%; p<0.05). For in vitro study, the other animals were killed and their thyroids were incubated with 125I. Thyroids explants from LepA and LepC groups presented lower thyroid 125I content (-32% and -29% p<0.05, respectively). The amount of our data suggest that, in vitro, leptin causes a direct inhibition of the rat thyroid RAIU, but in vivo, the effect of leptin was different according to the treatment period, which indicates that other indirect mechanisms are involved in the in vivo leptin chronic stimulation of the thyroid gland.
de Oliveira
Elaine
E
Department of Physiological Sciences, Roberto Alcantara Gomes Biology Institute, State University of Rio de Janeiro, Rio de Janeiro, Brazil.
Teixeira Silva Fagundes
Aline
A
Teixeira Bonomo
Isabela
I
Curty
Flavio Henrique
FH
Fonseca Passos
Magna Cottini
MC
de Moura
Egberto Gaspar
EG
Lisboa
Patrícia Cristina
PC
D000818:Animals; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007454:Iodides / Q000378:metabolism*; D007457:Iodine Radioisotopes; D020738:Leptin / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D027981:Symporters / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D013974:Thyroxine / Q000378:metabolism; D013997:Time Factors; D014284:Triiodothyronine / Q000378:metabolism; D000099209:Sodium-Iodide Symporters
D007454:Iodides; D007457:Iodine Radioisotopes; D020738:Leptin; D027981:Symporters; D013974:Thyroxine; D014284:Triiodothyronine; D000099209:Sodium-Iodide Symporters