Ca2+ pathway involved in the refilling of store sites in rat adrenal medullary cells.
It has been suggested that store-operated Ca(2+) entry (SOC) facilitates catecholamine secretion and synthesis in bovine adrenal medullary (AM) cells. However, there has been no experimental result clearly showing that cation channel activity is enhanced by store Ca(2+) depletion. Thus the present experiments were undertaken to address the issue of whether rat AM cells have SOC channels. Inhibition of the sarco(endo)plasmic reticulum Ca(2+) (SERCA) pump resulted in a sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in rat AM cells. This increase was completely suppressed by 2 mM Ni(2+) but not by 100 muM D600. A bath application of Ni(2+), but not D600, produced an outward current at -60 mV in rat AM cells, whereas exposure to a SERCA pump inhibitor did not affect either the whole cell current level or the Ni(2+)-induced outward current. The refilling of intracellular store sites was suppressed by the addition of Ni(2+) to the perfusate. RT-PCR revealed that transcripts for transient receptor potential channels 1 (TRPC1) and 5 (TRPC5) were present in rat adrenal medullas. Immunocytochemistry showed that TRPC1 channels, which have been implicated in SOC in certain types of cells, were mainly localized in the endoplasmic reticulum (ER) and not in the plasma membrane, and that STIM1, a Ca(2+) sensor in the ER, was not expressed in rat AM cells. On the basis of these results, we conclude that rat AM cells lack the SOC mechanism.
Matsuoka
Hidetada
H
Dept. of Cell and Systems Physiology, School of Medicine, Univ. of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
Harada
Keita
K
Ikeda
Tomoya
T
Uetsuki
Kouta
K
Sata
Takeyoshi
T
Warashina
Akira
A
Inoue
Masumi
M
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002395:Catecholamines / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004558:Electric Stimulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D008564:Membrane Potentials; D009532:Nickel / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002395:Catecholamines; D004791:Enzyme Inhibitors; D007211:Indoles; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels; C503500:Trpc5 protein, rat; C096351:transient receptor potential cation channel, subfamily C, member 1; D005711:Gallopamil; D019284:Thapsigargin; D009532:Nickel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid