Summary of results obtained from single ventricular myocytes.

Rats (8 weeks old) were fed the control diet or the Mg-deficient diet for 4–6 weeks, and [Mg2+]i was measured with the fluorescent indicator furaptra in the myocytes isolated from control rats (Control) and Mg-deficient rats (Mg-deficient). Each data represents mean ± SEM from the number of cells indicated in parentheses. The basal level of [Mg2+]i was measured either at 1 mM [Mg2+]o (i.e., Ca2+-free Tyrode’s solution) or at 0.2 mM [Mg2+]o (Mg2+ concentration of Ca2+-free Tyrode’s solution was reduced to 0.2 mM). Mg2+ influx rates were estimated by two different methods: the rates of Mg2+ loading (as shown in Fig. 3) and the rates of Mg2+ recovery after depletion (as shown in Fig. 1). The Mg2+ efflux rate was estimated from the initial rate of decrease in [Mg2+]i in the Mg2+-loaded cells as shown in Fig. 4. There was no significant difference between values obtained from control rats and those obtained from Mg-deficient rats.