RELEASE OF CA2-VEIN MYOCYTES( BY NORADRENALINE AND ATP FROM THE SAME CA2+ STORE SENSITIVE TO BOTH INSP(3) AND CA2+ IN RAT PORTAL)

Citation
P. Pacaud et G. Loirand, RELEASE OF CA2-VEIN MYOCYTES( BY NORADRENALINE AND ATP FROM THE SAME CA2+ STORE SENSITIVE TO BOTH INSP(3) AND CA2+ IN RAT PORTAL), Journal of physiology, 484(3), 1995, pp. 549-555
Citations number
18
Categorie Soggetti
Physiology
Journal title
ISSN journal
00223751
Volume
484
Issue
3
Year of publication
1995
Pages
549 - 555
Database
ISI
SICI code
0022-3751(1995)484:3<549:ROCMBN>2.0.ZU;2-Z
Abstract
1. Changes in cytosolic free Ca2+ concentration ([Ca2+](i)) induced by noradrenaline (NA) and ATP were investigated using indo-1 microspectr ofluorimetry in single smooth muscle cells of rat portal vein. 2. Acti vation of P-2x-purinoceptors by ATP (10 mu M) increased [Ca2+](i) from 92 +/- 7 nM (n = 18) to 557 +/- 30 nM (n = 11). In the presence of NS (10 mu M), the ATP-induced rise in [Ca2+](i) was reduced to 23.6 +/- 1.5% (n = 7) of the control response (in the absence of NA). 3. Tetrac aine (10 mu M to 2 mM) inhibited in a concentration-dependent manner t he Ca2+-induced Ca2+ release (CICR) evoked by 5 mM caffeine. In the pr esence of 1 mM tetracaine, the rise in [Ca2+](i) induced by ATP (10(-8 )-10(-4) M) was strongly inhibited. A tetracaine-resistant rise in [Ca 2+](i), corresponding to 26.4 +/- 2.3% (n = 14) of control values, was recorded in response to 10 mu M ATP. 4. The amplitude of the NA-induc ed [Ca2+](i) rise depended on NE concentrations (10(-8)-10(-5) M) and was not modified by tetracaine (1 mM). 5. This study suggests that Ca2 + ions released through the InsP(3) receptor-channel upon NA applicati on do not activate CICR and that the InsP(3)- and Ca2+-sensitive Ca2store appears to represent, at least functionally, a single releasable Ca2+ pool.