We studied the Ca2+ movement induced by activation of α1A-, α1B- and α1D-adrenoceptor subtypes in transfected HEK-293 cells with the fura- probe. All these α1-AR subtypes induced both Ca2+ release and Ca2+ entry. The effect on Ca2+ release in α1b transfected HEK-293 cells was bigger than that in α1a and α1b transfected HEK-293 cells, and the effects on Ca2+ entry were the same in ala, alb and aid transfected HEK-293 cells. The Ca2+ entry was inhibited by 1mM NiSO4, but not by nifedipine. Cyclopiazonic acid (CPA) produced a biphasic Ca2+ signal response in Ca2+ medium, and only induced a transient response in Ca2+-free medium. After depletion of CPA-sensitive Ca2+ pool by 10uM CPA in Ca2+-free medium, 10uM adrenaline (Adr) still transiently increased [Ca2+]i in three different α1-adrenoceptor subtype transfected HEK-293 cells. However, after depletion of drenaline-sensitive Ca2+ pool by 10uM Adr, CPA transiently elevated [Ca2+], only in ala and aid transfected HEK-293 cells, not in a,, transfected HEK-293 cells. U73122, a phospholipase C (PLC) inhibitor, inhibited both Ca2+ release and Ca2+ entry induced by activation of α1B-AR,α1B and α1D subtypes in transfected HEK-293 cells. These results suggest that HEK-293 cell line contains two functionally separate intracellular Ca2+ pools, CPA-sensitive and Adr-sensitive pools. Activation of a,,-AR stimulates Ca2+ release from both CPA-sensitive and Adr-sensitive Ca2+ pools. α1A and α1D subtypes induce Ca2+release only from Adr-sensitive Ca2+ pool.