Produção Nacional
Revisado por pares
Circadian and circannual rhythms of T3 and T4 secretions in Polwarth–Ideal rams
2002; Elsevier BV; Volume: 46; Issue: 1 Linguagem: Inglês
10.1016/s0921-4488(02)00103-7
ISSN1879-0941
AutoresM.I.L Souza, Sony Dimas Bicudo, Luiz Fernando Uribe-Velásquez, A. A. Ramos,
Tópico(s)Reproductive Physiology in Livestock
ResumoPlasma concentrations of triiodothyronine (T3) and thyroxine (T4) in five adult Polwarth–Ideal rams located at latitude 22°51′S and longitude 48°26′W were evaluated every 2 months for 1 year (June, August, October, December, February, April). Blood collections were made at 2 h intervals for 24 h in each month, and hormone determinations were by radioimmunoassay. Means of T3 (97.52±21.45 ng/dL) and T4 (4.30±0.94 μg/dL) varied in peaks throughout the 24 h period with the highest concentrations occurring in the afternoon (16:30 and 14:30 h, respectively), and throughout the year where the highest levels were during months of long daylengths (October, December, February). Results suggest circadian and circannual rhythms in thyroid hormone secretion may be present in rams kept relatively close to the equator.
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