Characterization of the intracellular Ca(2+) pools involved in the calcium homeostasis in Herpetomonas sp. promastigotes.
Trypanosomatids of the genus Herpetomonas comprises monoxenic parasites of insects that present pro- and opisthomastigotes forms in their life cycles. In this study, we investigated the Ca(2+) transport and the mitochondrial bioenergetic of digitonin-permeabilized Herpetomonas sp. promastigotes. The response of promastigotes mitochondrial membrane potential to ADP, oligomycin, Ca(2+), and antimycin A indicates that these mitochondria behave similarly to vertebrate and Trypanosoma cruzi mitochondria regarding the properties of their electrochemical proton gradient. Ca(2+) transport by permeabilized cells appears to be performed mainly by the mitochondria. Unlike T. cruzi, it was not possible to observe Ca(2+) release from Herpetomonas sp. mitochondria, probably due to the simultaneous Ca(2+) uptake by the endoplasmic reticulum. In addition, a vanadate-sensitive Ca(2+) transport system, attributed to the endoplasmic reticulum, was also detected. Nigericin (1 microM), FCCP (1 microM), or bafilomycin A(1) (5 microM) had no effect on the vanadate-sensitive Ca(2+) transport. These data suggest the absence of a Ca(2+) transport mediated by a Ca(2+)/H(+) antiport. No evidence of a third Ca(2+) compartment with the characteristics of the acidocalcisomes described by A. E. Vercesi et al. (1994, Biochem. J. 304, 227-233) was observed. Thapsigargin and IP(3) were not able to affect the vanadate-sensitive Ca(2+) transport. Ruthenium red was able to inhibit the Ca(2+) uniport of mitochondria, inducing a slow mitochondrial Ca(2+) efflux, compatible with the presence of a Ca(2+)/H(+) antiport. Moreover, this efflux was not stimulated by the addition of NaCl, which suggests the absence of a Ca(2+)/Na(+) antiport in mitochondria.
Sodré
C L
CL
Departamento de Bioquímica Médica, UFRJ, RJ, Brazil.
Moreira
B L
BL
Nobrega
F B
FB
Gadelha
F R
FR
Meyer-Fernandes
J R
JR
Dutra
P M
PM
Vercesi
A E
AE
Lopes
A H
AH
Scofano
H M
HM
Barrabin
H
H
D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000968:Antimycin A / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D004072:Digitonin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D007202:Indicators and Reagents / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D018942:Macrolides; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D019831:Sodium-Calcium Exchanger / Q000502:physiology; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014351:Trypanosomatina / Q000737:chemistry* / Q000502:physiology; D014475:Uncoupling Agents / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D007476:Ionophores; D018942:Macrolides; D009840:Oligomycins; D019831:Sodium-Calcium Exchanger; D014475:Uncoupling Agents; D012430:Ruthenium Red; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000001:Calcimycin; D014638:Vanadates; D000244:Adenosine Diphosphate; D000968:Antimycin A; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; C040929:bafilomycin A1; D004072:Digitonin; D002118:Calcium