[Role of the cell surface in the stimulation of cell multiplication]

Fertilization of eggs and effects of many growth factors on the membrane receptors of the cultured somatic cells induce similar changes in the plasma membrane transport properties, which determine changes in Ca2+ and H+ concentrations in the cytoplasm. The data are discussed which favour the concept that Ca2+ and H+ are secondary messengers of growth-stimulating influences and control many intracellular processes related to cell multiplication.