Immunohistological Localization and Expression of α-Actin in the Baboon (Papio anubis) Corpus Luteum

• Published in: The journal of histochemistry and cytochemistry Vol. 45; no. 1; pp. 71 - 77
• Main Authors: Khan-Dawood, Firyal S., Yang, Jun, Dawood, M. Yusoff
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01-01-1997
• Subjects: Actins - analysis; Animals; Blotting, Western; Cells, Cultured; Chorionic Gonadotropin - pharmacology; Corpus Luteum - blood supply; Corpus Luteum - chemistry; Epithelium - chemistry; Female; Granulosa Cells - chemistry; Immunohistochemistry; Luteal Cells - chemistry; Luteal Phase; Menstrual Cycle; Muscle, Smooth - chemistry; Ovary - chemistry; Papio; Progesterone - analysis; Theca Cells - chemistry; Western analysis; Corpus luteum; Immunohistology; Primate; Cytoskeleton; α-actin; Baboon; Cell-cell communication
• ISSN: 0022-1554; 1551-5044
• DOI: 10.1177/002215549704500110

We have recently shown the presence of E-cadherin and of α- and γ-catenins in human and baboon corpora lutea. These are components of adherens junctions between cells. The cytoplasmic catenins link the cell membrane-associated cadherins to the actin-based cytoskeleton. This interaction is necessary for the functional activity of the E-cad-herins. Our aim therefore was to determine the presence of α-actin in the baboon corpus luteum, to further establish whether the necessary components for E-cadherin activity are present in this tissue. An antibody specific for the smooth muscle isoform of actin, α-actin, was used for these studies. The results using immunohistochemistry show that (a) α-actin is present in steroidogenic cells of the active corpus luteum, theca externa of the corpus luteum, cells of the vasculature, and the tunica albuginea surrounding the ovary. The intensity of immunoreactivity for α-actin varied, with the cells of the vasculature reacting more intensely than the luteal cells. A difference in intensity of immunoreactivity was also observed among the luteal cells, with the inner granulosa cells showing stronger immunoreactivity than the peripheral theca lutein cells. There was no detectable immunoreactivity in the steroidogenic cells of the atretic corpus luteum. However, in both the active and atretic corpora lutea, α-actin-positive vascular cells were dispersed within the tissue. (b) Total α-actin (luteal and non-luteal), as determined by Western blot analyses, does not change during the luteal phase and subsequent corpus luteum demise (atretic corpora lutea). (c) hCG stimulated the expression of α-actin and progesterone secretion by the early luteal phase (LH surge + 1–5 days) and midluteal phase (LH surge + 6–10 days) cells in culture, but only progesterone in the late luteal phase (LH surge + 11–15 days). The data show that α-actin is present in luteal cells and that its expression is regulated by hCG, thus suggesting that E-cadherin may form functional adherens junctions in the corpus luteum.