Luminal Ca(2+) and the activity of sarcoplasmic reticulum Ca(2+) pumps modulate histamine-induced all-or-none Ca(2+) release in smooth muscle cells.
We have studied histamine (HA)-evoked intracellular Ca(2+) release in single, freshly isolated myocytes from the guinea pig urinary bladder. Short applications of histamine (5 s) produced a thapsigargin (TG)-sensitive transient increase in intracellular calcium concentration ([Ca(2+)](i)). It was established that histamine and caffeine (Caff) released Ca(2+) from the same intracellular stores in these cells. Reducing the Ca(2+) content of internal stores by incubating cells with U-73343 or cyclopiazonic acid (CPA) inhibited the histamine-evoked Ca(2+) release in 69% and 60% of cells, respectively. Under these conditions, all cells released Ca(2+) in response to either caffeine or acetylcholine (ACh). However, decreasing internal Ca(2+) stores by removing external Ca(2+) inhibited histamine-induced Ca(2+) mobilization in only 22% of cells. A similar small fraction of cells was inhibited when sarcoplasmic reticulum (SR) Ca(2+) pumps were quickly blocked to avoid a significant reduction of luminal Ca(2+). In conclusion, lowering the luminal Ca(2+) content in combination with an impairment of the SR Ca(2+) pump activity significantly diminishes the ability of histamine to evoke an all-or-none intracellular Ca(2+) release.
Rueda
Angélica
A
Departamento de Bioquímica, CINVESTAV-IPN, Apdo. Postal 14-740, Mexico, D.F. 07000, Mexico.
García
Lucía
L
Guerrero-Hernández
Agustín
A
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000502:physiology*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D007700:Kinetics; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D001743:Urinary Bladder / Q000378:metabolism
D004791:Enzyme Inhibitors; D004963:Estrenes; D006633:Histamine Antagonists; D007211:Indoles; D011760:Pyrrolidinones; C074854:U 73343; D006632:Histamine; D015544:Inositol 1,4,5-Trisphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D000109:Acetylcholine; D002118:Calcium; C000543:cyclopiazonic acid