Microfilaments interacting with heavy meromyosin and deoxyribonuclease I in cells of the ovarian follicle of a lizard.

Two types of filaments (microfilaments 4--6 nm in diameter, and intermediate filaments 7--10 nm in diameter) are common in the surface epithelial cells and theca fibroblasts of vitellogenic ovarian follicles of the lizard Anolis carolinensis. Heavy meromyosin (HMM), which forms complexes with actin filaments, interacts only with the microfilaments of theca fibroblasts. After myosin extraction of follicles no filaments disappeared, but when this treatment was followed by incubation with deoxyribonuclease I (DNA-ase I), which depolymerizes F-actin to G-actin, microfilaments disappeared from the theca fibroblasts. It is concluded that microfilaments in theca fibroblasts are actin-like and may contract to provide the mechanism of expulsion for the oocyte during ovulation. The intermediate filaments of the surface epithelial cells and theca fibroblasts may serve as a skeletal system for the large (up to 8 mm in diameter) vitellogenic follicle.