[Study on the relationship between intracellular free calcium and melanization in oocysts of Plasmodium yoelii].

OBJECTIVE: To study the change of intracellular free Ca2+ in the oocyst when it melanized and to find out the relationship between the melanized oocyst and its intracellular level of free Ca2+ in a Plasmodium-refractory strain of Anopheles dirus. METHODS: The distribution and experimental condition of the intracellular free Ca2+ in oocyst of Plasmodium yoelii was measured with Ca2+ sensitive dye Fluo-3/AM and Pluronic F-127 under confocal laser scanning microscope (CLSM) at different time. RESULTS: The best load condition was that the oocysts were incubated in 3 mumol/ml Fluo-3/AM adding 1 microliter/ml 25% Pluronic F-127 for 60 min at 37 degrees C. Fluorescent imaging of oocysts was affected by an increase or decrease of the concentration of Fluo-3/Am and incubation time. The distribution of intracellular free Ca2+ was heterogeneous in the oocysts. The mean value of Ca2+ in the mature oocysts was (137.15 +/- 7.02) nmol/L (X +/- S) but was (18.44 +/- 1.75) nmol/L in melanized oocysts with Ca2+ sedimentation in the wall of oocyst. CONCLUSION: The results suggest that the level of the intracellular free Ca2+ in oocyst decreased and excreted during its melanization in a Plasmodium-refractory anopheline mosquito species.