open access

Vol 43, No 1 (2005)
ORIGINAL PAPERS
Published online: 2011-08-19
Submitted: 2011-12-19
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Atresia of large ovarian follicles of the rat

Zbigniew Tabarowski, Maria Szołtys, Małgorzata Bik, Maria Słomczyn´ ska
Folia Histochem Cytobiol 2005;43(1):43-50.

open access

Vol 43, No 1 (2005)
ORIGINAL PAPERS
Published online: 2011-08-19
Submitted: 2011-12-19

Abstract

In the rat, at the beginning of pregnancy a cohort of antral follicles develops until the preovulatory stage. However, these follicles, differentiating in the hyperprolactinemic milieu, produce only small amount of estradiol, do not ovulate and undergo rapid degeneration. They constitute an interesting physiological model of atresia. In the present study, we analysed the development and subsequent degeneration of such follicles. The study was performed on Wistar female rats killed in succession between days 1-9 of pregnancy. Excised ovaries were submitted to a routine histological procedure. Paraffin sections were subjected to hematoxylin and eosin staining or in situ DNA labelling. Histological and TUNEL staining revealed that the investigated group of follicles grew slower than that on the corresponding days of the estrous cycle and reached a preovulatory size and morphological appearance on day 5 of pregnancy. They did not ovulate and between days 6 and 9 of pregnancy an increasing number of apoptotic cells appeared within these follicles. They were localized predominantly in the antral granulosa layer, especially near the cumulus oophorus complex (COC) and in the region linking the COC with the follicular wall. The COC and the theca layer were much less affected. In late stages of atresia, also cumulus cells became apoptotic but degenerating oocytes did not exhibit positive TUNEL staining. Only limited number of the theca cells have undergone apoptosis and generally they were not hypertrophied. Our findings indicate that much smaller than normal amount of intrafollicular estradiol was sufficient to support a normal, according to the morphological criteria, although slower development of antral follicles to the late preovulatory stage.

Abstract

In the rat, at the beginning of pregnancy a cohort of antral follicles develops until the preovulatory stage. However, these follicles, differentiating in the hyperprolactinemic milieu, produce only small amount of estradiol, do not ovulate and undergo rapid degeneration. They constitute an interesting physiological model of atresia. In the present study, we analysed the development and subsequent degeneration of such follicles. The study was performed on Wistar female rats killed in succession between days 1-9 of pregnancy. Excised ovaries were submitted to a routine histological procedure. Paraffin sections were subjected to hematoxylin and eosin staining or in situ DNA labelling. Histological and TUNEL staining revealed that the investigated group of follicles grew slower than that on the corresponding days of the estrous cycle and reached a preovulatory size and morphological appearance on day 5 of pregnancy. They did not ovulate and between days 6 and 9 of pregnancy an increasing number of apoptotic cells appeared within these follicles. They were localized predominantly in the antral granulosa layer, especially near the cumulus oophorus complex (COC) and in the region linking the COC with the follicular wall. The COC and the theca layer were much less affected. In late stages of atresia, also cumulus cells became apoptotic but degenerating oocytes did not exhibit positive TUNEL staining. Only limited number of the theca cells have undergone apoptosis and generally they were not hypertrophied. Our findings indicate that much smaller than normal amount of intrafollicular estradiol was sufficient to support a normal, according to the morphological criteria, although slower development of antral follicles to the late preovulatory stage.
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Keywords

Apoptosis; Preovulatory follicles; Hyperprolactinemia; Rat

About this article
Title

Atresia of large ovarian follicles of the rat

Journal

Folia Histochemica et Cytobiologica

Issue

Vol 43, No 1 (2005)

Pages

43-50

Published online

2011-08-19

Bibliographic record

Folia Histochem Cytobiol 2005;43(1):43-50.

Keywords

Apoptosis
Preovulatory follicles
Hyperprolactinemia
Rat

Authors

Zbigniew Tabarowski
Maria Szołtys
Małgorzata Bik
Maria Słomczyn´ ska

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