Functional state of cultured chick embryo cell mitochondria investigated in situ

The cell membrane of cultured chick embryo cells is permeable to Ca²⁺ after treatment with mannitol. Ca²⁺ uptake by mannitol-treated cells can be attributed to the mitochondria. $\text{Ca}{}^{\mathrm{2+}}\text{O}$ quotients and acceptor control ratios of such cells and isolated mitochondria are identical.Digitonin exerts two time-dependent effects on mannitol-treated cells: it increases the maximum extent of Ca²⁺ uptake by 5 – 20 percent. It also partially uncouples respiration from Ca²⁺ accumulation.It is suggested that mannitol treatment of cultured cells provides an easy way to study Ca²⁺ uptake by mitochondria $\text{in situ}$.