Efeitos da melatonina nos níveis de IGF-I e esteroides sexuais e no sistema reprodutor (ovários e útero) de ratas adultas
Arquivos
Data
2007
Autores
Dair, Elisabete Lilian 
Orientadores
Soares Júnior, José Maria
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
A pineal é aceita como reguladora da reprodução em mamíferos, por sua
capacidade de interagir com as gonadotrofinas e influenciar as gônadas e promover
a ciclicidade estral em algumas espécies. Contudo, sua função em espécies não
foto-periódicas (camundongo, rato, macaco e ser humano) ainda não está
totalmente esclarecida. Por este motivo, propusemo-nos a avaliar a histomorfologia
e a histomorfometria do sistema reprodutor (ovários e útero), bem como os níveis
plasmáticos de IGF-I e dos esteróides sexuais em ratas pinealectomizadas ou
mantidas sob estímulo luminoso contínuo e após o tratamento com melatonina.
Foram utilizadas ratas albinas, adultas, virgens, pesando aproximadamente
250g, da linhagem EPM - 1 Wistar. As ratas foram divididas, aleatoriamente, em seis
grupos, a saber: GI – controle, tratado com veículo (n=20); GII – falsamente
pinealectomizado, sham, tratado com veículo (n=20); GIII – pinealectomizado e
tratado com veículo (n=20); GIV - pinealectomizado e tratado com melatonina
(n=20); GV - submetido à luz contínua e tratado com veículo (n= 20); GVI –
submetido à luz contínua e tratado com melatonina (n=20). O tratamento com
melatonina (GIV e GVI) foi realizado por 90 dias consecutivos. Na noite anterior ao
término do estudo, os animais foram colocados em gaiolas metabólicas, coletandose
a urina noturna. Posteriormente, o sangue foi retirado pelo plexo ocular nos
animais para determinação hormonal. Em seguida, as ratas foram sacrificadas e os
ovários e o útero foram removidos para análise histomorfológica e histomorfométrica.
Observou-se que a redução dos níveis séricos da melatonina (pela
pinealectomia ou luz contínua, grupos III e V, respectivamente) determinou elevação
sérica de estrogênio e redução significante de progesterona e IGF-I. Já a reposição
com melatonina, reverteu este estado nos animais pinealectomizados, mas não nos
animais sob luz contínua (grupo VI). Houve diminuição dos níveis androgênicos nos animais que receberam melatonina (grupos IV e VI) em relação os animais com
baixos níveis de melatonina (grupos III e V).
A diminuição sérica de melatonina (grupos III e V) determinou a proliferação
do endométrio. Este efeito não foi totalmente bloqueado nos animais submetidos à
luz contínua ou à pinealectomia e que foram tratados com melatonina. A diminuição
dos níveis de melatonina determina alterações histomorfológicas e
histomorfométricas nos ovários, sendo que a reposição de melatonina restaura
essas modificações nos folículos ovarianos, bem como no epitélio e no estroma
(células intersticiais). Contudo, o efeito desse hormônio tem menor impacto no
epitélio superficial do ovário dos animais sob luz contínua.
Nossos dados sugerem que a melatonina interfere com a produção hormonal e
o sistema reprodutor, mas não é efetiva em animais sob luz contínua; possivelmente
outros mecanismos que possam estar envolvidos sejam independentes da pineal.
The pineal gland is accepted as the reproduction modulator in mammals but its function in non-photoperiodic species (mouse, rat and primate) is still not thoroughly clear considering the endocrine interactions are fairly complex. For this reason, we have proposed to evaluate the histomorphology of the reproductive system (ovary and uterus) as well as the plasmatic levels of IGF-I and the sexual steroids in pinealectomized female rats or kept under continuous luminous stimulus and after the treatment using melatonin. The albino virgo female rats weighed approximately 250g from the EPM lineage – 1 Wistar were randomly divided into six groups: GI – control treated with vehicle (n=20); GII – falsely pinealectomized, sham, and treated with vehicle (n=20); GIII – pinealectomized and treated with vehicle (n=20); GIV – pinealectomized and treated with melatonin (n=20); GV – submitted to continuous light and treated with vehicle (n=20); GVI – submitted to continuous light and treated with melatonin (n=20). The treatment using melatonin for these groups lasted 90 consecutive days. The night before the end of the study, the animals were put in metabolic cages to collect urine. Later, the blood was taken through the ocular plexus for the hormonal determination. Then, both the ovary and the uterus of the female rats were removed for a histomorphological and histomorphometric analyses. The reduction of the serum levels of melatonin (pinealectomy or continuous light) as followed by an increase in estrogen levels and a significant reduction in progesterone and IGF-I blood levels. Differently, the replacement with melatonin reverted this condition in the pinealectomized animals but this did not happen with the animals exposed to continuous light. There was a reduction in the androgenic levels when compared to animals with low levels of melatonin. The reduction in serum melatonin is related to the endometrial proliferation. This effect is not totally blocked in animals submitted to continuous light or pinealectomy, which were treated with melatonin. Also, the decrase in the melatonin levels determined histomorphologic changes in the ovaries and the melatonin replacement restored these alterations in the ovarian follicle as well as in the epithelium and in the ovarian stroma (interstitial cells). Nevertheless, the effect of this hormone has a smaller impact in the ovarian superficial epithelium in animals under continuous light. Our data suggest that melatonin interferes with the hormone production and the reproductive system, but this is not the case in animals under continuous light; it is possible that other mechanisms, which may be involved are regardless of the pineal.
The pineal gland is accepted as the reproduction modulator in mammals but its function in non-photoperiodic species (mouse, rat and primate) is still not thoroughly clear considering the endocrine interactions are fairly complex. For this reason, we have proposed to evaluate the histomorphology of the reproductive system (ovary and uterus) as well as the plasmatic levels of IGF-I and the sexual steroids in pinealectomized female rats or kept under continuous luminous stimulus and after the treatment using melatonin. The albino virgo female rats weighed approximately 250g from the EPM lineage – 1 Wistar were randomly divided into six groups: GI – control treated with vehicle (n=20); GII – falsely pinealectomized, sham, and treated with vehicle (n=20); GIII – pinealectomized and treated with vehicle (n=20); GIV – pinealectomized and treated with melatonin (n=20); GV – submitted to continuous light and treated with vehicle (n=20); GVI – submitted to continuous light and treated with melatonin (n=20). The treatment using melatonin for these groups lasted 90 consecutive days. The night before the end of the study, the animals were put in metabolic cages to collect urine. Later, the blood was taken through the ocular plexus for the hormonal determination. Then, both the ovary and the uterus of the female rats were removed for a histomorphological and histomorphometric analyses. The reduction of the serum levels of melatonin (pinealectomy or continuous light) as followed by an increase in estrogen levels and a significant reduction in progesterone and IGF-I blood levels. Differently, the replacement with melatonin reverted this condition in the pinealectomized animals but this did not happen with the animals exposed to continuous light. There was a reduction in the androgenic levels when compared to animals with low levels of melatonin. The reduction in serum melatonin is related to the endometrial proliferation. This effect is not totally blocked in animals submitted to continuous light or pinealectomy, which were treated with melatonin. Also, the decrase in the melatonin levels determined histomorphologic changes in the ovaries and the melatonin replacement restored these alterations in the ovarian follicle as well as in the epithelium and in the ovarian stroma (interstitial cells). Nevertheless, the effect of this hormone has a smaller impact in the ovarian superficial epithelium in animals under continuous light. Our data suggest that melatonin interferes with the hormone production and the reproductive system, but this is not the case in animals under continuous light; it is possible that other mechanisms, which may be involved are regardless of the pineal.
Descrição
Citação
DAIR, Elisabete Lilian. Efeitos da melatonina nos níveis de IGF-I e esteroides sexuais e no sistema reprodutor (ovários e útero) de ratas adultas. 2007. 110 f. Tese (Doutorado em Ciências) – Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, 2007.