valinomycin and Cell-Transformation--Neoplastic

Differences between transformed cells and their normal counterparts were defined by analyzing the cells' three-dimensional distribution of mass. Variables called factors, which explained the covariance of the real variables, were extracted from the data. We found that factors #4 (sharp, tapering projections) and #12 (rounding up), corresponded to G-protein functions. Then, the signature-type mass distribution of transformed cells was defined by factor values. Agents that caused signature-type mimicry could quantitatively shift factor values, for example, those affecting endocytic processing disproportionately reduced values of #4. Signature-type reversal was also observed and may be valuable in predicting the efficacy of chemotherapeutic agents.

Topics: Animals; Cell Line; Cell Transformation, Neoplastic; Colchicine; Insulin; Microtubules; Monensin; Paclitaxel; Phenotype; Rats; Tetradecanoylphorbol Acetate; Valinomycin

The effect of submicromolar concentrations of the K+ ionophore valinomycin on proliferation, viability, distribution of cell population over phases of the cell cycle, and cellular adenosine triphosphate content of different permanent rodent cell lines in vitro was investigated. Valinomycin inhibits proliferation of all cell lines tested with a saturating effect at about 20 to 100 nM. The effect of valinomycin on nontransformed 3T3 mouse and Rat-1 cells is nontoxic, whereas it acts with increasing toxicity on the transformed cells in the order 3T6 mouse, polyoma-3T3 mouse, temperature-sensitively Rous sarcoma virus-transformed Rat-1 at permissive temperature, and SV40-3T3 cells. According to these and some other criteria, the essential action of valinomycin appears to be to impose on the cells at low growth densities a state of limiting growth condition which normally is encountered only at high cell densities and/or low serum concentration. Nontransformed cells are proliferation arrested by valinomycin essentially in the G1 phase of the cell cycle, whereas all transformed cells under this condition are not arrested selectively in G1. In all cell lines tested (3T3, 3T6, and SV40-3T3), cellular adenosine triphosphate content is decreased by about 33% upon treatment with 20 nM valinomycin. Evidence is presented for a mitochondrial site of action of valinomycin.

Topics: Adenosine Triphosphate; Animals; Calcium; Cell Cycle; Cell Division; Cell Line; Cell Survival; Cell Transformation, Neoplastic; Dose-Response Relationship, Drug; Fibroblasts; Mice; Mitochondria; Rats; Valinomycin

Selectively permeable membrane vesicles isolated from Simian virus 40-transformed mouse fibroblasts catalyzed Na+ gradient-coupled active transport of several neutral amino acids dissociated from intracellular metabolism. Na+-stimulated alanine transport activity accompanied plasma membrane material during centrifugation in discontinuous dextran 110 gradients. Carrier-mediated transport into the vesicle was demonstrated. When Na+ was equilibrated across the membrane, countertransport stimulation of L-[3H]alanine uptake occurred in the presence of accumulated unlabeled L-alanine, 2-aminoisobutyric acid, or L-methionine. Competitive interactions among neutral amino acids, pH profiles, and apparent Km values for Na+ gradient-stimulated transport into vesicles were similar to those previously described for amino acid uptake in Ehrlich ascites cells, which suggests that the transport activity assayed in vesicles is a component of the corresponding cellular uptake process. Both the initial rate and quasi-steady state of uptake were stimulated as a function of a Na+ gradient (external Na+ greater than internal Na+) applied artificially across the membrane and were independent of endogenous (Na+ + K+)-ATPase activity. Stimulation by Na+ was decreased when the Na+ gradient was dissipated by monensin, gramicidin D or Na+ preincubation. Na+ decreased the apparent Km for alanine, 2-aminoisobutyric acid, and glutamine transport. Na+ gradient-stimulated amino acid transport was electrogenic, stimulated by conditions expected to generate an interior-negative membrane potential, such as the presence of the permeant anions NO3- and SCN-. Na+-stimulated L-alanine transport was also stimulated by an electrogenic potassium diffusion potential (K+ internal greater than K+ external) catalyzed by valinomycin; this stimulation was blocked by nigericin. These observations provide support for a mechanism of active neutral amino acid transport via the "A system" of the plasma membrane in which both a Na+ gradient and membrane potential contribute to the total driving force.

Topics: Amino Acids; Biological Transport, Active; Cations, Monovalent; Cell Line; Cell Membrane; Cell Transformation, Neoplastic; Endoplasmic Reticulum; Fibroblasts; Gramicidin; Hydrogen-Ion Concentration; Kinetics; Ouabain; Potassium; Simian virus 40; Sodium; Temperature; Valinomycin

Topics: 4-Chloromercuribenzenesulfonate; Amino Acids; Animals; Biological Transport, Active; Cell Line; Cell Membrane; Cell Transformation, Neoplastic; Fibroblasts; Kinetics; Membrane Potentials; Mice; Models, Biological; Monensin; Nigericin; Potassium; Simian virus 40; Sodium; Species Specificity; Valinomycin

It was shown that repeated administrations of valinomycin in doses of 1.0 and 0.01 gamma/gm to mice with Ehrlich ascitic tumors inhibited the ascite development. The radioautographic study using 3H-thimidine showed that 24 hours after the administration of valinomycin in doses of 0.1 and 0.01 gamma/gm transference of the cells into the phase of DNA synthesis was inhibited--inhibition of the tumor cell mitotic activity took place.

Topics: Animals; Body Weight; Carcinoma, Ehrlich Tumor; Cell Transformation, Neoplastic; Depression, Chemical; DNA, Neoplasm; Mice; Mitosis; Neoplasm Transplantation; Thymidine; Time Factors; Tritium; Valinomycin