TEMPERATURE-INDUCED RAPID INCREASE IN CYTOPLASMIC FREE CA2-DONOVANI PROMASTIGOTES( IN PATHOGENIC LEISHMANIA)

We demonstrate that the cytoplasmic free Ca2+ concentration in three v irulent Leishmania donovani promastigote strains is maintained at 20-3 0 nM level whereas the avirulent promastigotes maintain [Ca2+](i) at 8 0-100 nM. Rapid exposure of virulent promastigotes to higher physiolog ical temperature increases [Ca2+](i) many-fold, Use of CaCl2, EGTA and Mn2+ confirmed that both release of Ca2+ from internal pool(s) and in flux from outside milieu are responsible for this increase in [Ca2+](i ). Application of oligomycin, CN-, and nigericin indicated the nonmito chondrial pH(i) sensitive pool as the possible intracellular origin fo r internal Ca2+ release, Exposure of these cells to acidic environment had no influence on [Ca2+](i). In contrast, the avirulent promastigot es or freshly isolated amastigotes had shown no effect of heat-shock o r pH shock on [Ca2+](i) of these cells, Our results indicate that the upward shift in temperature may play a role in signal transduction eve nts in morphogenetic transformation of L. donovani promastigotes that involves mobilization of Ca2+ in cytoplasm.