The effect of Ca2+ on virus-cell fusion and permeability changes.

Sendai virus-mediated permeability changes in Lettre cells or red blood cells are affected by extracellular Ca2+ in the following way: the lag period to onset of permeability changes is lengthened and the subsequent extent of leakage is reduced. Ca2+ neither stimulates nor inhibits fusion of the viral envelope to the plasma membrane of Lettre cells or red blood cells. It is concluded that Ca2+ protects cells against virally-induced permeability changes in a manner not involving membrane fusion.