Taurine effects on the transition temperature in Arrhenius plots of ATP-dependent calcium ion uptake in rat retinal membrane preparations.

The transition temperatures calculated from Arrhenius plots of ATP-dependent calcium ion uptake in rat retinal membrane preparations differed depending upon the presence or absence of exogenous taurine. At a constant calcium ion concentration of 10 microM and in the absence of taurine the transition temperature was 17.9 +/- 4.9 degrees, whereas in the presence of 20 mM taurine the transition temperature was raised to 25.4 +/- 0.8 degrees. Arrhenius plots of maximum velocities of calcium ion uptake (calculated from six calcium ion concentrations which varied from 5 to 300 microM) also demonstrated a taurine effect on the transition temperatures (13.5 degrees vs 25.5 degrees). In addition, taurine lowered the apparent activation energy for calcium ion uptake.