Hamster thecal cells express muscle characteristics
Contraction of the follicular wall about the time of ovulation appears to be a coordinated event; however, the cells that mediate it remain poorly studied. We examined the theca externa cells in the wall of hamster follicles for the presence of a functional actomyosin system, both in developing foll...
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Published in | Biology of reproduction Vol. 39; no. 1; pp. 119 - 130 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Madison, WI
Society for the Study of Reproduction
01.08.1988
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Subjects | |
Online Access | Get full text |
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Summary: | Contraction of the follicular wall about the time of ovulation appears to be a coordinated event; however, the cells that
mediate it remain poorly studied. We examined the theca externa cells in the wall of hamster follicles for the presence of
a functional actomyosin system, both in developing follicles and in culture. We used a monoclonal antibody (HHF35) that recognizes
the alpha and gamma isoelectric variants of actin normally found in muscle, but not the beta variant associated with non-muscle
sources, to evaluate large preovulatory follicles for actin content and composition. Antibody staining of sectioned ovaries
showed intense circumferential reactivity in the outermost wall of developing follicles. Immunoblots from two-dimensional
gels of theca externa lysates demonstrated the presence of the two muscle-specific isozymes of actin. Immunofluorescence of
cultured follicular cells pulse-labeled with [3H] thymidine (for autoradiographic detection of DNA replication) revealed the
presence, in many dividing cells, of actin filaments aligned primarily along the longitudinal axis of the cells. In cultures
exposed to the calcium ionophore A23187 (10(-4) M) for varying periods (5 min to 1 h), contraction of many individual muscle-actin-positive
cells was observed. Immunofluorescence of these cells, fixed immediately after ionophore-induced contraction, revealed compaction
of the actin filaments. Our findings demonstrate that the cells of the theca externa contain muscle actins from an early stage
and that these cells are capable of contraction even while proliferating in subconfluent cultures. They suggest that follicular
growth may include a naturally occurring developmental sequence in which a contractile cell type proliferates in the differentiated
state. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-3363 1529-7268 |
DOI: | 10.1095/biolreprod39.1.119 |