Two Mechanisms in Cell Adhesion Revealed by Effects of Divalent Cations

Abstract

The effect of divalent cations on cell-to-cell and cell-to-substrate adhesions was studied using two different types of chicken embryonic cells (fibroblastic and neural retina cells). Mn²⁺, Co²⁺, Mg²⁺ and Ca²⁺ were effective in promoting the aggregation of fibroblastic cells, while Sr²⁺ and Ba²⁺ were not effective. Among these ions, Ca²⁺ showed some unique effects on cell aggregation. Aggregation was initiated immediately after the addition of Mn²⁺, Co²⁺ or Mg²⁺ whereas with Ca²⁺ a lag period was always observed. When the medium contained both Ca²⁺ and Mg²⁺, the aggregate size formed was bigger than that formed with either ion at an equimolar concentration. The divalent cation dependence of fibroblastic cell adhesion to non-cellular substrate was essentially the same as that of cell-to-cell adhesion. The aggregation of neural retina cells specifically depended on the presence of Ca²⁺. For adhesion of neural retina cells to non-cellular substrate, however, Ca²⁺ was not effective, and only Mn²⁺ or Co²⁺ was effective. These results suggest two different mechanisms in cell adhesion.