Phospholipase A(2) is involved in thapsigargin-induced sodium influx in human lymphocytes.
Previously, we reported that emptying of intracellular Ca(2+) pools with endoplasmatic Ca(2+)-ATP-ase inhibitor thapsigargin leads to the Na(+) influx in human lymphocytes (M. Tepel et al., 1994, J. Biol. Chem. 269, 26239-26242). In the present study we examined the mechanism underlying the thapsigargin-induced Na(+) entry. We found that the thapsigargin-induced increase in Na(+) concentration was effectively inhibited by three structurally unrelated phospholipase A(2) (PLA(2)) inhibitors, p-bromophenacyl bromide, 3-(4-octadecyl)-benzoylacrylic acid (OBAA), and bromoenol lactone (BEL). The thapsigargin-induced Na(+) influx could be mimicked by PLA(2) exogenously added to the lymphocyte suspension. In addition, thapsigargin stimulated formation of arachidonic acid (AA), the physiological PLA(2) product. AA induced Na(+) entry in a time- and concentration-dependent fashion. Both, thapsigargin-induced Na(+) influx and AA liberation were completely inhibited in the presence of tyrosine kinase inhibitor genistein but not in the absence of extracellular Ca(2+). Collectively, these data show that thapsigargin-induced Na(+) entry is associated with tyrosine kinase-dependent stimulation of PLA(2).
Nofer
J R
JR
Institut für Klinische Chemie und Laboratoriumsmedizin, Zentrallaboratorium, Westfälische Wilhelms-Universität, A. Schweitzer Str 33, Münster, 48-149, Germany.
Junker
R
R
Walter
M
M
Seedorf
U
U
Assmann
G
G
Zidek
W
W
Tepel
M
M
D000098:Acetophenones / Q000494:pharmacology; D000179:Acrylates / Q000494:pharmacology; D016718:Arachidonic Acid / Q000097:blood; D001565:Benzoates / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003022:Clotrimazole / Q000494:pharmacology; D004464:Econazole / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007700:Kinetics; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D009637:Masoprocol / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000097:blood*; D011753:Pyrones / Q000494:pharmacology; D012964:Sodium / Q000097:blood*; D019284:Thapsigargin / Q000494:pharmacology*
D000098:Acetophenones; D000179:Acrylates; D001565:Benzoates; D009281:Naphthalenes; D010726:Phosphodiesterase Inhibitors; D011753:Pyrones; C069438:3-(4-octadecyl)benzoylacrylic acid; D016718:Arachidonic Acid; D019284:Thapsigargin; D004464:Econazole; D009637:Masoprocol; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D012964:Sodium; D010741:Phospholipases A; D003022:Clotrimazole; C006821:4-bromophenacyl bromide; D007213:Indomethacin