title: Role of the F-actin cytoskeleton in the RVD and RVI processes in Ehrlich ascites tumor cells.
abstract: The role of the F-actin cytoskeleton in cell volume regulation was studied in Ehrlich ascites tumor cells, using a quantitative rhodamine-phalloidin assay, confocal laser scanning microscopy, and electronic cell sizing. A hypotonic challenge (160 mOsm) was associated with a decrease in cellular F-actin content at 1 and 3 min and a hypertonic challenge (600 mOsm) with an increase in cellular F-actin content at 1, 3, and 5 min, respectively, compared to isotonic (310 mOsm) control cells. Confocal visualization of F-actin in fixed, intact Ehrlich cells demonstrated that osmotic challenges mainly affect the F-actin in the cortical region of the cells, with no visible changes in F-actin in other cell regions. The possible role of the F-actin cytoskeleton in RVD was studied using 0. 5 microM cytochalasin B (CB), cytochalasin D (CD), or chaetoglobosin C (ChtC), a cytochalasin analog with little or no affinity for F-actin. Recovery of cell volume after hypotonic swelling was slower in cells pretreated for 3 min with 0.5 microM CB, but not in CD- and ChtC-treated cells, compared to osmotically swollen control cells. Moreover, the maximal cell volume after swelling was decreased in CB-treated, but not in CD- or Chtc-treated cells. Following a hypertonic challenge imposed using the RVD/RVI protocol, recovery from cell shrinkage was slower in CB-treated, but not in CD- or Chtc-treated cells, whereas the minimal cell volume after shrinkage was unaltered by either of these treatments. It is concluded that osmotic cell swelling and shrinkage elicit a decrease and an increase in the F-actin content in Ehrlich cells, respectively. The RVD and RVI processes are inhibited by 0.5 microM CB, but not by 0.5 microM CD, which is more specific for actin.
authors.affiliation: Biochemistry Department, August Krogh Institute, Copenhagen, DK-2100, Denmark. sfpedersen@aki.ku.dk
authors.forename: S F
authors.initials: SF
authors.lastname: Pedersen
authors.forename: J W
authors.initials: JW
authors.lastname: Mills
authors.forename: E K
authors.initials: EK
authors.lastname: Hoffmann
mesh_terms: D000199:Actins / Q000502:physiology*; D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000473:pathology* / Q000503:physiopathology*; D048429:Cell Size / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology*; D005456:Fluorescent Dyes; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D051379:Mice; D018613:Microscopy, Confocal; D009997:Osmotic Pressure; D010590:Phalloidine; D012235:Rhodamines; D014407:Tumor Cells, Cultured
chemical_list: D000199:Actins; D005456:Fluorescent Dyes; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D012235:Rhodamines; D010590:Phalloidine