Em. Lammel et al., TRYPANOSOMA-CRUZI INVOLVEMENT OF INTRACELLULAR CALCIUM IN MULTIPLICATION AND DIFFERENTIATION, Experimental parasitology, 83(2), 1996, pp. 240-249
The possible role of intracellular Ca2+ level on Trypanosoma; cruzi di
fferentiation was explored. The addition to epimastigotes of a Triatom
a infestans intestinal homogenate, which that triggers off tile differ
entiation to the infective metacyclic form, induced a sudden rise in [
Ca2+](i) from the basal value, 94 +/- 28 to 584 +/- 43 nmole/liter. Th
is increase was not affected by the presence of EGTA in the medium. Tr
ypsin-treated intestinal homogenate did not alter the [Ca2+](i) of epi
mastigotes. Calmodulin inhibitors (Calmidazolium, Trifluoperazine, and
Chlorpromazine) blocked differentiation. Although the calcium ionopho
re ionomycin increased [Ca2+](i) to 342 +/- 29 nmole/liter, it was una
ble to induce differentiation by itself. BAY K8644 and Methoxyverapami
l (agonist and antagonist of Ca2+ channels, respectively) were unable
to affect [Ca2+](i) by themselves, or when added to stimulated parasit
es, and did not exert a stimulatory or inhibitory effect on morphogene
sis. BAPTA/AM, a Ca2+ chelator, partially blocked the rise in [Ca2+](i
) and morphogenesis; this effect was reversed by ionomycin. The requir
ement of intracellular Ca2+ on epimastigote multiplication was also ev
aluated. The addition of EGTA to the culture medium led to a decrease
in epimastigote multiplication till it practically ceased in the sixth
passage. When such parasites were transferred to LIT they partially r
ecovered the growth rate. Parasites from passages III, IV, and V in th
e Ca2+-depleted medium maintained their basal [Ca2+](i), but when trea
ted with the intestinal homogenate, the rise in [Ca-2+](i) was abrogat
ed, Accordingly, the differentiation percentages of such parasites dro
pped significantly completed With controls. (C) 1996 Academic Press, I
nc.