Figure 1.

Mg²⁺ concentration dependence of ⁴⁵Ca²⁺ uptake in ER microsomes isolated from male rat brain. Net ⁴⁵Ca²⁺ accumulation was measured by liquid scintillation counting after the uptake reaction was allowed to proceed for 60 minutes at 37°C in buffer containing 300 nM free Ca²⁺ and 2 mM ATP (see materials and methods). Data are means ± SEM, n = 3.