Localization of actin and myosin in the rat oocyte and follicular wall by immunofluorescence

Abstract

The distribution of actin and myosin in the rat ovary at different stages of postnatal development was studied by examination of cryostat sections treated with antibodies to chicken smooth muscle (gizzard) myosin or to chicken (pectoral muscle) actin and subsequently with fluoresceinated goat anti-rabbit gamma-globulins. Staining with either antiserum revealed several layers of intensely fluorescent elongated cells within the theca externa, forming a coherent band around the larger Graafian follicles. In smaller follicles, this band of fluorescent cells was incomplete, and ovaries of immature (6-day-old) rats were devoid of strongly fluorescent cells. Corpora lutea contained only scattered fluorescent cells at their circumference. Sections of mature ovaries incubated with antibodies raised against striated (pigeon pectoral) muscle myosin generated no significant fluorescence. Large oocytes stained with either anti-actin or anti-smooth muscle myosin showed a thin fluorescent band just beneath the zona pellucida, suggesting that actin and myosin are associated with the oolemma. The distribution of the two antigens in serial sections of follicles coincided, suggesting that the same cells contained both actin and myosin. It is suggested that follicular growth and maturation is attended by the development of a smooth muscle layer in the theca and that contraction of this layer in response to catecholamines and/or prostaglandins may play a role in the extrusion of the oocyte. The role of contractile elements in the oocyte remains to be elucidated.

Early Follicular Development and Atretic Changes in the Ovary of the Lamb? Fine Structure and Histochemistry

“…These probably are associated with the retraction of the microvilli which occurs subsequently during both maturation and atresia (Odor 1960;Hertig and Barton 1973). Actin and myosin have been reported as being present in rat oocytes near the oolemma (Amsterdam et al 1977).…”

Immunohistochemical Demonstration of a Myosin-Like Protein in the Oocyte

“…At the present time only some hypotheses may be considered : that an acto-myosin-like system is engaged in the mechanism of cytokinesis in eggs (9) ; that an acto-myosin-like system is involved during early cleavage divisions in eggs (8) and that an acto-myosin-like system is involved in spindle rotation and extrusion of polar body (1).…”

“…But the observations of these authors (1) are not accurate on the cellular localization of the contractile proteins.…”

“…As to the presence of contractile elements in a mammalian oocyte the information is limited to the observations of Amsterdam et al (1) which suggest the presence of an actin-like and of a myosin-like protein in the rat oocyte. But the observations of these authors (1) are not accurate on the cellular localization of the contractile proteins.…”

Structure-Function Relationships in the Wall of the Ovarian Follicle

“…Relevant ultrastructural features include parallel bundles of microfilaments about 6 nm in diameter associated with characteristic dense bodies (fusiform densities), some degree of basal lamina formation, and foci of specific cell-to-cell attachment. Further evidence of the myoid nature of many theca externa cells derives from the demonstration by immunofluorescence of thecal binding of antibodies to actin and smooth muscle myosin (Kapinus and Rukosuev 1975;Amsterdam et al 1977;Walles et al 1978). Species in which myoid theca externa cells have now been demonstrated include the rat, Rhesus monkey, sheep, rabbit, cat, mouse, guinea pig, man, gerbil, cow (see Espey 1978), and more recently the hamster (Pendergrass and Talbot 1979) and pig (Patterson and O'Shea 1980).…”