Arachidonic acid-induced calcium influx in human platelets. Comparison with the effect of thrombin.
The effects of arachidonic acid and thrombin on calcium movements have been studied in fura-2-loaded platelets by a procedure which allows simultaneous monitoring of the uptake of manganese, a calcium surrogate for Ca2+ channels, and the release of Ca2+ from intracellular stores. Arachidonic acid induced both Ca2+ (Mn2+) entry through the plasma membrane and Ca2+ release from the intracellular stores. The release of Ca2+ was prevented by cyclo-oxygenase inhibitors and mimicked by the prostaglandin H2/thromboxane A2 receptor agonist U46619. Ca2+ (Mn2+) entry required higher concentrations of arachidonic acid and was not prevented by either cyclo-oxygenase or lipoxygenase inhibitors. Several polyunsaturated fatty acids reproduced the effect of arachidonic acid on Ca2+ (Mn2+) entry, but higher concentrations were required. The effects of maximal concentrations of arachidonic acid and thrombin on the uptake of Mn2+ were not additive. Both agonists induced the entry of Ca2+, Mn2+, Co2+ and Ba2+, but not Ni2+, which, in addition, blocked the entry of the other divalent cations. However, arachidonic acid, but not thrombin, increased a Ni2(+)-sensitive permeability to Mg2+. The effect of thrombin but not that of arachidonic acid was prevented either by pretreatment with phorbol ester or by an increase in cyclic-AMP levels. Arachidonic acid also accelerated the uptake of Mn2+ by human neutrophils, rat thymocytes and Ehrlich ascites-tumour cells.
Alonso
M T
MT
Departamento de Fisiología y Bioquímica, Facultad de Medicina, Universidad de Valladolid, Spain.
Sanchez
A
A
Garcia-Sancho
J
J
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005452:Fluoresceins; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008345:Manganese / Q000097:blood / Q000378:metabolism; D009637:Masoprocol / Q000494:pharmacology; D051379:Mice; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D051381:Rats; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*
D001095:Arachidonic Acids; D005230:Fatty Acids, Nonesterified; D005231:Fatty Acids, Unsaturated; D005452:Fluoresceins; D005456:Fluorescent Dyes; D011450:Prostaglandin Endoperoxides, Synthetic; D016718:Arachidonic Acid; D008345:Manganese; D004533:Egtazic Acid; D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D009637:Masoprocol; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D013917:Thrombin; D001241:Aspirin; D002118:Calcium; D016257:Fura-2