Abstract: 　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 Plutonic F-127 under confocal laser scanning microscope (CLSM) at different time. Results The best load condition was that the oocysts were incubated in 3 μmol/ml Fluo-3/AM adding 1 μl/ml 25% Pluronic F-127 for 60 min at 37 ℃ . 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-reiractory anopheline mosquito species.

Key words: Plasmodium yoelii, oocyst, nnelanization, Ga2+, CLSM