Asymmetrical, agonist-induced fluctuations in local extracellular [Ca(2+)] in intact polarized epithelia.
We recently proposed that extracellular Ca(2+) ions participate in a novel form of intercellular communication involving the extracellular Ca(2+)-sensing receptor (CaR). Here, using Ca(2+)-selective microelectrodes, we directly measured the profile of agonist-induced [Ca(2+)]ext changes in restricted domains near the basolateral or luminal membranes of polarized gastric acid-secreting cells. The Ca(2+)-mobilizing agonist carbachol elicited a transient, La(3+)-sensitive decrease in basolateral [Ca(2+)] (average approximately 250 microM, but as large as 530 microM). Conversely, carbachol evoked an HgCl2-sensitive increase in [Ca(2+)] (average approximately 400 microM, but as large as 520 microM) in the lumen of single gastric glands. Both responses were significantly reduced by pre-treatment with sarco-endoplasmic reticulum Ca(2+) ATPase (SERCA) pump inhibitors or with the intracellular Ca(2+) chelator BAPTA-AM. Immunofluorescence experiments demonstrated an asymmetric localization of plasma membrane Ca(2+) ATPase (PMCA), which appeared to be partially co-localized with CaR and the gastric H(+)/K(+)-ATPase in the apical membrane of the acid-secreting cells. Our data indicate that agonist stimulation results in local fluctuations in [Ca(2+)]ext that would be sufficient to modulate the activity of the CaR on neighboring cells.
Caroppo
R
R
Dipartimento di Fisiologia Generale ed Ambientale, Università di Bari, Via Amendola 165/A, 70126 Bari, Italy.
Gerbino
A
A
Debellis
L
L
Kifor
O
O
Soybel
D I
DI
Brown
E M
EM
Hofer
A M
AM
Curci
S
S
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D002118:Calcium / Q000819:agonists* / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D002614:Chelating Agents / Q000494:pharmacology; D004396:Coloring Agents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D016257:Fura-2 / Q000494:pharmacology; D005753:Gastric Mucosa / Q000378:metabolism; D007150:Immunohistochemistry; D007811:Lanthanum / Q000494:pharmacology; D008627:Mercuric Chloride / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011898:Ranidae; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D015398:Signal Transduction
D000891:Anti-Infective Agents, Local; D002614:Chelating Agents; D004396:Coloring Agents; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D008627:Mercuric Chloride; D007811:Lanthanum; D002217:Carbachol; D000251:Adenosine Triphosphatases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2