Acute effects of taurine on intracellular calcium in normal and diabetic cardiac myocytes

The present study investigated the acute effects of taurine on intracellula r Ca2+ ([Ca2+](i)) in normal and diabetic cardiac myocytes. [Ca2+](i) was m onitored using fura-2 in single myocytes isolated from control or streptozo tocin-treated rats and paced at frequencies between 0.33 Hz and 2.0 Hz in t he absence or presence of 20 mM taurine. Increasing stimulus frequency resu lted in significant increases in resting and peak [Ca2+](i), and amplitude of the Ca2+ transient in both control and diabetic myocytes. The amplitude of the Ca2+ transient and the extent of its increase with increasing freque ncy was, however, significantly lower in the diabetic myocytes. Taurine sig nificantly increased resting [Ca2+](i), peak [Ca2+](i), and the amplitude o f the Ca2+ transient in both control and diabetic myocytes at all stimulus frequencies examined. The degree of potentiation of the Ca2+ transient decr eased with increasing stimulus frequency in control cells but not in diabet ic cells. In the absence of taurine the decay of the Ca2+ transient was sig nificantly slower in diabetic than control myocytes. Taurine was without si gnificant effect on the time course of the Ca2+ transient decay in control cells, however, in diabetic cells it significantly accelerated the rate of decay. The data demonstrate directly that taurine is able to increase [Ca2](i) and the amplitude of the Ca2+ transient in both normal and diabetic ca rdiac myocytes. In addition several of the effects of taurine appeared to b e more pronounced in diabetic than control cells.