Adhesion of Sarcoma I cells (SaI) to untreated or to serum-treated glass was examined by layering 51Cr-labeled cells on the substrate for 20 min at 34°C and determining the glass-bound radioactivity after the monolayers were rinsed. Adhesion to untreated glass proceeded in sodium chloride-imidazole-potassium medium (SIK) without added divalent cations, whereas SaI adhered maximally to the serum-coated substrate only in the presence of 50 µM or more Mn. Divalent Mg, Ca, Co, Ni, or Zn were inactive or minimally active. Mn-stimulated adhesion was sharply temperature dependent, reversible upon removal of Mn, and inhibited by Ca as well as by cytochalasin B, vinblastine, or tetracaine. Adhesion of SaI in SIK did not ensue when cells or the coated substrate were pretreated with Mn and washed in SIK before the adhesion assays. Microscope observations showed that Mn induced the formation of cell processes, ruffles, and veils, and that SaI spread on the uncoated or serum-coated substrate when exposed to Mn. Cells withdrew veils and processes and rounded up when postincubated in Mn-free medium. Formation of cell processes and spreading was inhibited by cytochalasin B, vinblastine, or tetracaine. Manganese-induced adhesion seems to require the participation of microtubules and microfilaments and may be mediated by an effect of Mn on Ca fluxes. The results support the role of cell processes and spreading in cell-to-substrate adhesion.

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