A dual effect of arachidonic acid on Ca2+ transport systems in lymphocytes.
A sustained increase of cytoplasmic Ca2+ concentration ([Ca2+]i) in lymphocytes was induced by a potent inhibitor of the intracellular Ca(2+)-pump 2,5-di-(tert-butyl)-1,4-hydroquinone (BHQ) that effectively depletes Ca2+ stores and produces Ca2+ influx. The addition of low concentrations of arachidonic acid (AA) (less than 10 microM) in the presence of a BHQ-induced Ca2+ response produced a [Ca2+]i decrease. At the same time at higher concentrations, AA induced an additional increase of [Ca2+]i. The unidirectional uptake of Mn2+ into fura-2 loaded thymocytes was used to examine the effects of AA and BHQ on Ca2+ permeability of the plasma membrane. Judging by the rate of Mn(2+)-induced fura-2 fluorescence quenching, AA causes a concentration-dependent increase of the divalent cations' permeability both in the control solution and in the presence of BHQ. These results allowed us to suggest that the decrease of BHQ-induced [Ca2+]i stationary levels caused by low AA concentrations is due to the enhancement of Ca2+ extrusion from the cell, whereas the additional [Ca2+]i increase at high AA concentrations results from an elevation of cell membrane Ca2+ permeability.
Khodorova
A B
AB
Institute of Biotechnology, Moscow, Russian Federation.
Astashkin
E I
EI
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D016718:Arachidonic Acid / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D005456:Fluorescent Dyes; D016257:Fura-2; D006873:Hydroquinones / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013950:Thymus Gland / Q000166:cytology
D000975:Antioxidants; D005456:Fluorescent Dyes; D006873:Hydroquinones; C019359:2,5-di-tert-butylhydroquinone; D016718:Arachidonic Acid; D008345:Manganese; D002118:Calcium; D016257:Fura-2