The
cations Ca2+ and K+ and the
anions Cl-, HCO3-, and PO4- were studied for their contribution to metacyclic trypomastigote formation of Trypanosoma cruzi in
starvation media consisting of
phosphate-buffered saline (PBS) + 10 mM
proline + 10 mM
sodium acetate as well as one of the following
salts: 0.035% NaHCO3 (PBSNPA), 0.035%
K2CO3 (PBSKPA) or 0.035%
K2HPO4 (PBSPPA). Isolates CL and DM28c were activated to transform with 5% CO2 and the percent metacyclogenesis determined after incubation for 96 h in PBS
starvation media. Maximal metacyclogenesis was found with CaCl2 and KCl. In the presence of K+, the percent transformation was highest with the
phosphate salt, followed by the
carbonate and the
chloride salts. Cells incubated in PBSNPA and the cationic
ionophores A23187 (5 x 10(-6) M),
lasalocid (5 x 10(-6) M), and
valinomycin (10(-8) M) do not survive; addition of 2 mM CaCl2 or 17 mM KCl to DM28c cells, reversed the lethal action of the
ionophores permitting differentiation into metacyclic forms. The addition of CaCl2 to CL cells incubated in
ionophores abrogated the lethal effect of the
ionophores but transformation was significantly different than in control preparations. Adding KCl to
ionophore incubated cells resulted in normal levels of transformation except in the case of
valinomycin. DM28c and CL cells incubated in PBSKPA show significantly greater metacyclogenesis in the presence of 5 mM
EGTA. These results indicate that exogenous concentrations of several
cations and
anions significantly influence T. cruzi metacyclogenesis and that the degree of response by the parasite to free ion levels may be strain dependent.