Intracellular Ca2+ homeostasis in rat round spermatids.
Intracellular calcium, [Ca2+]i, can regulate meiotic progression of mammalian oocytes. However, the role of [Ca2+]i in the regulation of the spermatogenic process and its cellular homeostatic mechanisms in spermatogenic cells has not been elucidated. Using intracellular fluorescent probes for Ca2+ and immunodetection of plasma membrane (PM) Ca(2+)-ATPases, we report that: a) rat round spermatids maintain [Ca2+]i levels of 60 +/- 5 nM (SEM), as estimated with fluo-3 in single cells or fura-2 in cells in suspension; b) these cells regulate [Ca2+]i by actively extruding it using a PM Ca(2+)-ATPase; c) rat spermatids also actively transport Ca2+ by sarco-endoplasmic reticulum type ATPases (SERCA); d) rat spermatids possess non-mitochondrial intracellular Ca2+i stores insensitive to thapsigargin but releasable by ionomycin; and e) rat spermatids do not activate Ca2+ entry mechanisms by the release of Ca2+ from SERCA-regulated stores. These results demonstrate that rat round spermatids can generate modulated intracellular Ca2+ signals upon activation of Ca2+ channels or Ca2+ release from intracellular stores.
Berrios
J
J
Instituto de Quimica, Universidad Catolica de Valparaiso, Chile.
Osses
N
N
Opazo
C
C
Arenas
G
G
Mercado
L
L
Benos
D J
DJ
Reyes
J G
JG
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000032:analysis; D002454:Cell Differentiation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006706:Homeostasis; D007211:Indoles / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000494:pharmacology; D008540:Meiosis / Q000187:drug effects; D008565:Membrane Proteins / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013087:Spermatids / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013091:Spermatogenesis / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007211:Indoles; D007476:Ionophores; D008565:Membrane Proteins; D014638:Vanadates; D008345:Manganese; D015759:Ionomycin; D019284:Thapsigargin; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid