Toxoplasma gondii-vertebrate cell interactions. I. The influence of bicarbonate ion, CO2, pH and host cell culture age on the invasion of vertebrate cells in vitro.

A controlled-environment culture system was used to show that both physical and biologic parameters can influence the penetration of vertebrate cells by Toxoplasma gondii. The optimum bicarbonate ion concentration for the penetration of bovine embryo skeletal muscle (BESM) cells is 36.25 mM. Higher or lower bicarbonate ion concentrations are increasingly inhibitory to penetration. As CO2 increases in the range from 0.5-3.7 mM, penetration is progressively inhibited. No relationship was found between penetration and pH in the pH range of 6.949-7.765. The culture age of the BESM cells directly influenced the ability of the parasites to penetrate the cells. Older BESM cells were more refractory to penetration than younger cells.