In mammals, Ca2+ pumps use the chemical energy derived
from the hydrolysis of ATP to remove Ca2+ from the
cytoplasm of a variety of cell types. The pumps of plasma membranes
(PMCA family) and those of endoplasmic or sarcoplasmic reticulum
(SERCA family) have the same physiological functions, despite
differences in their structure, subcellular localization and
modulatory mechanisms. Thapsigargin, a plant-derived sesquiterpene
lactone, inhibits the activity of all of the SERCA isoenzymes
(SERCA1, SERCA2 and SERCA3) with
equal potency, but has no effect on the ATPase or transport activities
of PMCA pumps. In previous reports we demonstrated a
(Ca2+-Mg2+)ATPase activity coupled to the active
transport of Ca2+ in subcellular fractions from
Schistosoma mansoni . The aim of the present work was, first,
to investigate the subcellular localization of the
(Ca2+-Mg2+)ATPase activities present in
P1 and P4 fractions, using thapsigargin,
cyclopiazonic acid (CPA) and tamoxifen as inhibitors of
Ca2+ pump. Second, to investigate if an ATPase responsible
for the control of Ca2+ homeostasis, could be involved in
the molecular mechanism of praziquantel-induced contraction in S.
mansoni.
