Analytical Behavior of Fura-2 and Its Determination of [Ca^2＋ ]i in Lymphocytes Treated with Cefotaxime

The interaction of Fura-2 with Ca^2＋ is studied using steady fluorescence technique. The effect of pH on the spectra behavior of Fura-2 in the presence of Ca^2＋ is investigated, the excitation maxima （340 nm） and the isobestic point （360 nm） for the fluorescence spectra of Fura-2 depend on pH. At different temperatures the apparent dissociation constants （ Kd ） of Fura-2-Ca^2＋ complex are examined, Kd is found to decrease with increasing temperatures （20 ℃, 37 ℃, 50 ℃ ） and △His calculated to be 21.16 kJ/mol by using the Van＇ t Hoff equation at pH 7.4 for all the temperatures tested. The determination of intracellular Ca^2＋ concentration （ [Ca^2＋ ] i ） in lymphocyte is developed by using Fura-2 as a fluorescence probe in the presence of Cefotaxime at 37 ℃ and pH 7.4.