Effect of calcium, magnesium and temperature on praziquantel-induced tegument damage of the male Schistosoma japonicum

When male shistosomes were preincubated in Hank’s balanced salt solution(HBS) without calcium for 1 h, followed by the addition of praziquantel at the final concentration of 1 or 30 microg/mL, about half of the worms tested appeared intact while others showed some vesicles along their surface within 1h.After the addition of Ca2+(1.4 mM) to the media, all worms exhibited strong contraction and vesicles appeared along the tegument within 15-30 min. Preincubation of male schistosomes in HBS with 30 mM Mg2+ before the addition of praziquantel (1 or 30 microg/mL) prevented the formation of vesicles in about half of the worms tested within 1 h. At 4 degrees male schistosomes showed moderate contraction and praziquantel exhibited little activity on them, but once returned to 37 degrees, the worms recovered to normal. When male schistosomes were exposed to praziquantel( 1 or 30 mcirog/mL) in HBS at 4 degrees for 1-2 h, no vesicles were formed. However, when these worms were transferred to 37 degrees, a strong spasmodic contraction occurred and vesicles appeared along the tegument within 15-30 min.