Proliferação, apoptose e histomorfometria da glândula mamária de ratas tratadas com tiroxina na lactação e ao desmame e desenvolvimento dos filhotes

Abstract

RESUMOO objetivo deste estudo foi avaliar a histomorfometria e a taxa de proliferação e apoptose da glândula mamária de ratas tratadas com tiroxina pela imunoexpressão de CDC-47 e caspase-3, respectivamente. Também foi avaliado o desenvolvimento dos filhotes de ratas tratadas com tiroxina. Foram utilizadas 36 ratas distribuídas em dois grupos, tratado com tiroxina e controle. Após 60 dias de tratamento com tiroxina, as ratas foram acasaladas. Seis animais/grupo foram sacrificados no 2 o e 21 o dias de lactação e no 5 o dia após o desmame. Houve diferença significativa entre grupos apenas no quinto dia após o desmame. O tratamento com tiroxina aumentou a taxa de apoptose caracterizada pela maior expressão de caspase-3 nas células do epitélio mamário. As mães tratadas com tiroxina apresentaram comportamento alterado, mas não houve diferença significativa no que se refere aos cuidados com o filhote quanto a higienização e aquecimento. Levando-se em consideração o sexo e o tamanho da ninhada, os filhotes das ratas tratadas com tiroxina e controle não apresentaram diferença significativa de peso ao desmame. Conclui-se que a administração de baixas doses de tiroxina aumenta a taxa de apoptose, caracterizada pelo aumento da expressão de caspase-3 no epitélio mamário cinco dias após o desmame, mas não altera a taxa de proliferação celular e o comportamento materno. The purpose of this study was to evaluate mammary gland histomorphometry and proliferation rate and apoptosis of thyroxine-treated rats by CDC-47 and caspase-3 immunoexpression. The development of thyroxine-treated rats offspring was also evaluated. Thirty-six female rats were used, distributed in two groups, treated and non-treated with thyroxine. After 60 days of treatment, with thyroxine, rats were mated. Six animals/group were sacrificed on the 2 nd and 21 st days of lactation and on the 5 th day after weaning. A significant difference was observed between groups only on the 5 th day after weaning. Thyroxine treatment increased apoptosis rate, which was characterized by a higher caspase-3 expression in mammary epithelial cells. Thyroxine-treated mothers presented changed behavior, but there was no significant difference regarding taking care of offspring, as for cleaning offspring and keeping them warm. Taking into account sex and size of offspring, those from control and thyroxine-treated mothers presented no significant difference of weight and weaning. In conclusion, administering low doses of thyroxine increases apoptosis rate, which is characterized by the increased caspase-3 immunoexpression in mammary epithelial cells 5 days after weaning. But does not affect proliferation rate and development of thyroxine-treated rats offspring. (Arq Bras Endocrinol Metab 2007;51/6:1000-1006)

Histological and immunohistochemical characterization of the Mongolian gerbil’s mammary gland during gestation, lactation and involution

“…Watson (2006) stated that in mice, involution of the mammary epithelium was concluded six days after the 10-day post-partum forced weaning. In rats, the adipose tissue percentages at involution day 5, is statistically similar to that observed at the beginning of lactation (Leite et al, 2007). Thus, the mammary involution in the gerbils was quicker than in mice and rats, since the adipose tissue area percentages at post-weaning day 5 were very close to those shown at the beginning of gestation.…”

Aspectos morfológicos e fisiológicos de glândulas mamárias de fêmeas bovinas – revisão de literatura

“…Além disso, para que os principais hormônios galactopoéticos, tais como o GH e a PRL, atuem na glândula, é essencial a participação dos hormônios tireoidianos. O GH, a PRL e a T4 aumentam a atividade da 5'desiodase na glândula mamária, enzima que converte a tiroxina (T4) em triiodotironina (T3), forma metabolicamente ativa do hormônio tireoidiano (LEITE et al, 2007).…”

Administration of Thyroxine Affects the Morphometric Parameters and VEGF Expression in the Uterus and Placenta and the Uterine Vascularization but does Not Affect Reproductive Parameters in Gilts During Early Gestation

“…2005; Freitas et al. 2007; Leite et al. 2007, 2008) have demonstrated that thyroxine administration in female rats induces precocious sexual maturity, stimulates ovary folliculogenesis, reduces the follicular atresia, increases the ovulation and conception rates without altering foetal development and stimulates lactogenesis.…”