Mechanisms that regulate the amount of releasable Ca2+ in intracellular stores of cultured mouse astrocytes were investigated using digital imaging of fura‐2 loaded cells. At rest, the cytoplasmic Ca2+ concentration, (Ca2+)cyt, was about 110 nM. In the absence of extracellular Ca2+, cyclopiazonic acid (CPA), an inhibitor of the endoplasmic reticulum (ER) Ca2+‐ATPase, induced a transient, four‐fold increase in (Ca2+)cyt due to the release of Ca2+ from inositol triphosphate (IP3) sensitive stores. Caffeine (CAF), which releases Ca2+ from Ca2+‐sensitive stores, induced a two‐fold increase in (Ca2+)cyt. The CPA‐ and CAF‐sensitive stores could be released independently. Changes in the amplitudes of the Ca2+ transients were taken as a measure of changes in store content. Removal of extracellular Na+ or addition of ouabain, which inhibit Ca2+ extrusion and promote Ca2+ entry across the plasmalemma via the Na/Ca exchanger, caused minimal increases in resting (Ca2+)cyt but greatly potentiated both CPA‐ and CAF‐induced Ca2+ transients. The amount of Ca2+ releasable from the IP3 (CPA) sensitive store was directly proportional to cytosolic Na+ concentration (i.e., inversely proportional to the transmembrane Na+ electrochemical gradient). Under these reduced Na+ gradient conditions, little, if any, Ca2+ destined for the ER stores enters the cells through voltage‐dependent Ca2+ channels. These results demonstrate that mouse astrocytes contain two distinct ER Ca2+ stores, the larger, IP3‐ (CPA‐) sensitive, and the smaller, Ca2+‐ (CAF‐) sensitive. The Ca2+ content of both ER stores can be regulated by the Na/Ca exchanger. Thus, the magnitude of cellular responses to signals that are mediated by Ca2+ release induced by the two second messengers, IP3 and Ca2+, can be modulated by factors that affect the net transport of Ca2+ across the plasmalemma. © 1996 Wiley‐Liss, Inc.
Glia – Wiley
Published: Apr 1, 1996
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera