Efeito do hipotireoidismo induzido experimentalmente com methimazole sobre o testiculo de ratos de varias idades

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

Although it is well known that thyroidal hormones are involved in the development and maintenance of many organs, there remain several open questions as to their role in testicular physiology. The present work proposes to contribute to a better understanding of the role of thyroidal hormones in testicular maintenance. The evaluation was based on the biometric, morphologic and hormonal parameters of groups of data of different ages in which a previous experimental hypothyroidism was induced by treating them with daily 0,05mg Methimazole, and confirmed by measuring thyroxine levels. Our study involved an experimental of 68 white male rats and 12 foetuses (albino Rattus novergicus). These animals were subdivided into 6 experimental groups according to the period of treatment and their death date and will here be designated as mother-foetal ( 190 days of intrauterine life), 8 day old, 21 day old, 35 day old, 50 day old and 90 day old hypothyroidism, respectively. Our results showed that induction to hypothyroidism in the eighth day of pregnancy, which corresponds to the beginning of organogenesis in rats, did not result in any increase in the incidence of either foetal reabsorption nor congenital malformations, as well not causing behavioral alteration of animals with hypothyroidism. In all of the experimental groups considered, the treated animals have a significant reduction (p<0,05) in body weight as related to the control animals of same age. Biometric evaluation of testicles has shown that treated animals had significant reduction (p<0,05) in both the testicular weight and the diameter of seminiferous tubules as well as a reduction in the nuclear volume of Sertoli cells. Only the foetuses having 19 days of intrauterine life had no differences in such parameters, while in the treated 90 day old animals testicular recuperation was observed. As to the morphology, the testicular development of treated animals was delayed in the beginning of the seminiferous epithelium cycle, with a reduction in the quantity of germinative cells and an increase in the number of degenerated cells. In both the 50 and 90 day old experimental groups, the treated animals completed staging of the seminiferous epithelium, but the frequency of stages I, VII/VIII and XIV was reduced as compared to the control animals of the same age. Duplicated dosages of plasmic testosterone by means of solid phase fluoroimunoassays showed no significant differences in the values found for both treated and control animals. We conclude that hypothyroidism severely impairs espermatogenesis in young rats as indicated by the reduced testicular weight, the diminished seminiferous tubule diameter, the increased degeneration of germinative cells, the delayed staging in the seminiferous epithelium cycle and the reduced nuclear volume in Sertoli cell. This did not occur in adults rats. In treated animals belonging to the 90 day old experimental group we have observed the occurence of significantly larger gain in both the testicular weight and the seminiferous tubule diameter, as compared to the control animals of the same age, as well as the occurrence an apparent stabilization of the nuclear volume of Sertoli cells, which thereby suggest that there is no influence of the thyroidal hormones upon adult rats testicles

ASSUNTO(S)

sertoli espermatogenese em animais celulas de testiculos hipotireoidismo

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