Experiments aimed at testing the effect of Ca2+ on heat shock-induced changes in protein synthesis of cultured sugar beet cells were performed. Heat shock inhibits the synthesis of non-heat shock proteins (non-HSPs) and promotes the synthesis of a set of HSPs. Extracellular Ca2+ appeared to be strictly required for the synthesis of non-HSPs. Calcium was found to differentially exert its effect on the HSP synthesis: calcium induced (96 and 76 kDa), stimulated (94, 67, 58, 52, 32, 30, 26 and 22 kDa) or did not influence (82, 17 kDa) the de novo production of various HSPs. Cell injury increased if the cells were exposed to high temperature in a Ca(2+)-deficient medium. Calcium supplement to Ca(2+)-depleted cells resulted in the recovery of HSP synthesis and reduced cell injury by heat shock.