Evidence for a sodium/calcium exchanger and voltage-dependent calcium channels in adipocytes.
The objective of these studies is to identify and characterize Ca2+-transport systems that may be of potential importance in the action of Ca2+-mobilizing hormones in the adipocyte. Using the Ca2+-sensitive photoprotein, aequorin, [Ca2+]i was estimated to be 0.15 microM, assuming an intracellular [Mg2+] of 1 mM. Substitution of Na+ with choline+ caused a transient increase in [Ca2+]i which was inversely related to extracellular [Na+], consistent with operation of a mediated Na+-Ca2+ exchange system. The stoichiometry was 3Na+:Ca2+. Elevation of extracellular K+ caused an increase in [Ca2+]i that was blocked by the Ca2+ channel antagonist, diltiazem, by omitting extracellular Ca2+, or by substituting Sr2+ for Ca2+. These findings indicate the presence of an Na+-Ca2+ exchanger and voltage-sensitive Ca2+ channels in adipocytes.
Pershadsingh
H A
HA
Department of Laboratory Medicine, University of California, San Francisco 94143-0808.
Lee
L Y
LY
Snowdowne
K W
KW
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000331:Aequorin; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002794:Choline / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D004563:Electrochemistry; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger
D015220:Calcium Channels; D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D000331:Aequorin; D011189:Potassium Chloride; D012964:Sodium; D004110:Diltiazem; D002794:Choline; D002118:Calcium